Text and photos by George Franklin #20000416

1955-57 WHEEL TUBS

Materials Needed:Weld-thru primerMiscellaneous flat sheetmetal88-0187-1 Joint & Seam Sealer

Parts Needed:31-410 Wheel Tub Kit31-89 1956-57 Left Rear Wheelhouse Extension31-90 1956-57 Right Rear Wheelhouse Extension Optional Parts:31-317 1955-57 Left Trunk Wall Repair Panel

(Htp/Cvt Only)31-318 1955-57 Right Trunk Wall Repair Panel

(Htp/Cvt Only)31-223 1955-57 Complete Trunk Floor 31-276 1955-57 Complete Trunk Floor W/Braces

31-81 1955 Left Rear Wheelhouse Extension31-82 1955 Right Rear Wheelhouse Extension

To order parts call 1-800-456-1957 or visit ClassicChevy.com

Tools Needed: 1/4” pilot point drill bitDrillSeam splitterBall peen hammerMarkersCut-off toolReciprocating sawDie grinderSoap stoneMasking tape

Sharp knifeMeasuring tapeC-clampsPneumatic high speed sawBody hammer and dolliesTin snipsPneumatic hole punchMIG welderAlignment punch toolsVise-grips

My 1956 two-door sedan project car had some very rusty rearwheelhouses, wheel tubs, and trunk walls. The car is being customizedwith a street/strip flavor, so originality is not a big concern. It has alreadybeen treated to a spring pocket kit P/N 21-131 and is due for some verywide rear tires. This car needed so much sheet metal that the decisionwas made to use race car-style wheel tubs and to repair the trunk walls.The final result is a whopping 16" of tire width clearance between theinside of the quarter panel lip and the original frame.

Time Frame: 40-60 hours

31-90 31-410

Photo #3: With the rear of the carup on jack stands, remove bothrear wheels and the gas tank.Before cutting any sheet metalaway, mark the inside of theouter quarter panel along thelower edge of the wheelhouseseal. The new wheel tub mustmeet the quarter panel near thisline. Also mark the location anddepth of the window dimple inthe front wheelhouse section.This dimple allows necessary

clearance for the rear corner of the rear quarter window.

Photo #4a & 4b: A cut-off tool was used to sever the supportbetween the original inner wheel tub and the trunk hinge box.Always use proper safety equipment.

Photo #2: The tub kit P/N 31-410 has four nearly flat piecesof 24 gauge steel. Theseinclude two semi-circularcheeks and two rectangularbands. Also in the carton willbe two sheets of corrugatedpaper that will serve as bandtemplates. Do not destroy thecarton. It will be used to makethe cheek templates.

Photo #1: The trunkarea of this car was insad shape. The rearsection of the originalinner wheel tub hadrusted away from theinner trunk wall. Therusty gap was over aninch wide and hadbeen filled in by gobs

of body filler. The outer rear wheelhouse section between therear quarter panel and trunk wall didn't look any better.The front section of the original inner wheel tub had similarrust problems. The outer front wheelhouse section was rustyas well. Rather than purchase a few thousand dollars of sheetmetal to preserve the original look, the decision was made togo for a street/strip look for a lot less money. As one can see,this car had recently received a new floor. The rear seat backsupport will need to be removed to gain access to the tubs.Begin by drilling out the support spot welds with a 1/4 inchpilot point drill bit. Use a seam splitter to pop the welds loose,and remove the support.

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We used a reciprocating saw tocut the tub from the trunk floor.For the cuts along the inboardand rear sides of the tub, cut the

floor and leave the floor to tub flange attached to the tub. At the front of tub we preserved the outboard 8" of the floorflange to become an attachment point for the new tub. Drillout the spot welds holding the front of the tub to the floor.Use a seam splitter to separate the front side of the tub fromthe floor.

Photo #8: Workingfrom under the car,mark the underside ofthe trunk floor alongthe outboard edge ofthe frame. We areusing a flat soap stonewhich left a goodvisible line.

We used a cut-off tool to make cuts through the trunk floorevery few inches along the line.

Photo #5: This is thepreserved floor flangesection. This flange hasno holes drilled thoughit because this is abrand new floor andhad never been spotwelded to the originaltub. If your rearwheelhouse extensions (mud flaps) are in good shape you maywant to preserve them as well. Leave them attached to thequarter panel at the rear. Cut the extensions away from therear wheelhouse section with a horizontal cut at trunk floorheight. If your rear wheelhouse baffle is in good shape youmight wish to preserve it too. This baffle seals the upper innerquarter panel keeping dust, heat, cold, and tire smoke frommaking their way into the passenger compartment. The baffleis welded to the inner trunk wall and to the top of the rearouter wheelhouse. Cut the baffle away from the wheelhouse,leaving it attached to the trunk wall.

Photo #7: This was a good timeto remove the paint from thelower portion of the hinge boxusing a 3M Green Roloc bristledisc on a pneumatic die grinder.These discs are great forremoving paint without grindingaway too much metal. The metalon this car was already thinenough! The lower portion ofthe hinge box was then coatedwith weld-thru primer, SEM39783. Rather than repeatingthis many times, suffice it to say that all metal pieces need tobe clean and bare prior to welding. The metal should also becoated with weld-thru primer if the backside metal surface willnot be accessible after welding.

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Photo #9: On the top surface ofthe trunk floor the cuts wereconnected with a length of tapeto mark a continuous cut line.This cut will be parallel to anddirectly above the frame'soutboard edge.

Photo #6: These arethe removedcomponents of theoriginal sheet metalfrom the left side ofthe car. The smallpiece in the middle

is the baffle. This baffle was badly rusted and new ones arenot available for this body style. The baffle on the right sideof this car was missing entirely. New baffles will be fabricated.The piece on the far left is the original rear wheelhouseextension. It was in pretty good shape, but the right side oneon this car was missing. New extensions, P/N 31-89 and 31-90, will be used.

Photo #10: There are four verticalbeads rolled into the originalinner trunk wall for strength. Therear cut line on the trunk floor,marked here with tape, was justto the rear of the forward most(fourth) bead. This was a conser-vative initial position for the cut.The cut will be moved rearwardlater to allow fine tuning of theheight of the new tub. This reartrunk floor cut is perpendicular tothe frame.

Photo #15: Raise thecheek template upinto the opening inthe trunk floor withthe inch markings onthe inboard side. UseC-clamps to hold thetemplate to theframe. The centerline of the template

Photo #13: As therusted metal wasremoved we found theoriginal location of thebaffle. The arrow marksthat location, justforward of the hingebox on the outboardside of this panel. You

will want to mount the new baffle in this same location.

Photo #12: The rustedpart of the trunk wall mustalso be removed. We usedtape to mark a one inchborder around the rustededge. We cut along theoutside of this tape line inorder to reach solid metal.Cut away as much or aslittle metal as needed.

Photo #16: Measurefrom the cheektemplate to the insideof the quarter panel atevery inch mark aroundthe circumference.Keep the tape measureperpendicular to thecheek template andparallel to the ground.

Record these measurements on the cheek template. Thesemeasurements determine the width of the band.

Photo #14: Make a template ofthe tub cheek using the cartonthat the tub kit came in. Tracethe shape of the metal cheekonto the carton and cut thetemplate out with a sharp knife.Make a mark every inch alongthe circumference of thetemplate.

Photo #17: Curl the bandtemplate provided in the kitby rolling it around acylindrical object. Apropane bottle was usedhere.

Photo #18: Remove the cheektemplate from the car. Usemasking tape to attach the bandtemplate to the cheek template.Transfer the recorded measure-ments to the band and connectthem to mark a cut line along theband. In order to make trialfitting of the tub template easier,we cut the band about onequarter inch short of this line.

Photo #11: The front cut willalso be perpendicular to theframe and preserves theoutboard eight inches of theoriginal floor to the forwardinner wheel tub flange.

has been marked as a reference. Conventional wisdom is thatthe center line of racing tubs should be vertical and centeredon the rear axle. This gives maximum vertical clearance forsuspension travel and symmetrical front and rear tireclearance. We instead placed the center line behind the rearaxle and at an angle to vertical. This minimizes intrusion ofthe tub into the passenger compartment and retains properrear quarter window clearance, while still leaving plenty of tireclearance. The upper surface of the new tub should end upjust below the trunk hinge box, although it sits lower than inthis view. You can just see the hinge box at the top center ofthis photo. The conservative rear trunk floor cut made earliercan now be reassessed. By gradually moving this cut line tothe rear, the cheek template can rise higher in the trunk. Thegoal is for the cheek template to end up just below the trunkhinge box.

Photo #20: When the tubtemplate is properlylocated it will be belowand to the rear of thewindow dimple marking.This will allow properoperation of the rearquarter window. Alsomake sure the template

position will not interfere with holes used to attach theexterior stainless trim.

Photo #21: A contourmarking tool allowed us tomake a more accurateband fit. The tool wasmade from a woodenpaint paddle with holesdrilled at one and twoinches from its end.These holes allow the tip of a marker to pass through the tool.The contour tool was slid along the inner quarter marking aline on the underside of the band template. This marked linefollowed the exact contour of quarter panel and was exactlyone inch from that surface. If the band template was cut toonarrow, the two inch hole on the tool could be used instead.With the tub template in its final position this is a good time tomark the inboard side of the cheek template along the top ofthe trunk floor.

Photo #19: Working fromabove, place the tubtemplate in the trunk andattach it to the frame withC-clamps. The top of theband template should endup about 1/2 inch belowthe hinge box. The tubtemplate can be raised bygradually increasing the length of the trunk opening. Makingnew rear trunk floor cuts will allow this. Notice the final cut inthis photo is about 3" to the rear of the conservative initial cut.This final cut is just ahead of the third trunk wall bead.

Photo #23: We slid the end ofcheek lip into the band seamand bent the band up slightlywith a body hammer, lockingthe cheek into the seam. Tapthe seam up just enough tohold the cheek and bandtogether. Gradually work yourway down the seam locking ina few inches at a time.

Photo ##22: Next weassembled the actual steel tubby mating a band to a cheek.We rolled the band around aspare tire to give it a bit of acurve. Make sure the openpart of the Pittsburgh seam isto the inside of the curve. We

also ran a small screwdriver down the seam to make sure itwasn't pinched flat by the curving process. We used a hammerand dolly to check the lip on the curved edge of the cheek to

Photo #24: After the entirecircumference of the cheek islocked to the band, the seam canbe gradually flattened. Byworking a bit at a time the seamwill be flat and free of kinks.Finish the seam with a hammerand dolly.

Photo #25: The cheektemplate was then cutalong the line markingthe top of the trunkfloor. The piece of thecheek template cut awaywas saved to later serveas a guide for flangeconstruction. The tubtemplate was placed

inside the newly assembled metal tub and the trunk floor lineof the template was traced.

Photo #26: The contourtool was used to trace theexact contour of the innerquarter panel surfaceonto the band. The frontand rear edges of theband template weretraced as well. At thispoint a decision must tobe made on how theband will be attached to the inner surface of the rear quarterpanel. If these tubs are going into a car with a nice paint job,

make sure it had a nice 90 degree angle. The lip of the cheekfits into the seam on the band, so checking these areas first isrecommended. We also recommend at least two people forhandling this awkward job.

then this marked line will be a cut line, and the band will beglued and sealed to the quarter with autobody sealant alone.This car wasn't painted, so the decision was made to make tabsthat would allow spot welding of the band to the inner surfaceof the quarter panel. This method will be significantly strongerthan just using sealant alone. A second line was drawn usingthe contour tool, one inch further from the cheek than thefirst line. This second line became the cut line using apneumatic high speed saw. The cheek was then cut along theline marking the trunk floor surface. The front and rear edgesof the band were cut one inch long. These long edges willextend below the trunk floor when the tub is in place. Theywill become attachment points for the wheelhouse extensionat the rear and for a patch panel that will seal the passengercompartment floor and quarter panel at the front.

Photo #27: Tabswere made bycutting out triangleshaped pieces usingtin snips. Thetriangles were oneinch deep, one inchacross their bases,and one inch apart.

A pneumatic hole punch was used to make 3/16” holes for spotwelds, two inches apart. Pliers were used to bend the tabsdown along the first contour line and then the tabs wereflattened with a hammer and dolly. The cardboard templateshown was used to keep the tab spacing consistent.

Photo #28: Workingfrom above, the tubwas trial fitted to thecar. The top surfacewas checked with alevel. Make sure theband is behind andbelow the windowdimple and doesn’tinterfere with anytrim mounting holes. Slight adjustment of the tabs might benecessary to create a snug fit between the tub and the innersurface of the quarter panel. Be careful when moving the tubin and out of the trunk floor. The thin sheet metal tub caneasily bend or kink.

Photo #29: Using the shape ofthe original baffle as a guide, atemplate for a new baffle wascut from cardboard. Theplacement for the baffle will bejust rear of the peak of theband, insuring that water cannotbecome trapped against thebaffle as it is thrown up into therear tail light area by the tires.This template is purposefully cutlong with its lower edge belowthe line marking the

wheelhouse seal. The lower edge will be trimmed for a tight fitto the top of the band.The new baffle was cut from a flat piece of 18 gauge sheetmetal. It was tack welded to the quarter panel and to trunkwall with a MIG welder. The tub was then fitted and the loweredge of the baffle was trimmed for a tight fit to the band. Oncewe were satisfied with the fit, the baffle was sealed along itsupper edge with sealer P/N 88-0187-1. After the tub iswelded into place and the trunk wall is repaired, the rest of theperimeter of the baffle can be sealed.

Photo #30a & 30b: The underside of the trunk floor along thecut lines was cleaned to bare metal and the tub was loweredinto place one final time. When the fit was satisfactory the tubwas tack welded to the trunk floor from underneath. The bandwas tack welded to the baffle from above.A few of the tabs were spot welded to the inside of the quarterpanel. The line marking the edge of the wheelhouse seal is nolonger visible in this photo. That surface was prepped and isnow covered in a layer of weld-thru primer.

Photo #31: More tackwelds were addedalong the floor tocheek edge.

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Photo #32a & 32b: Theportion of the cheektemplate that was cutaway and saved becamea trunk floor contourguide for making aflange. The flange willhelp strengthen thejoint between the floor

and the tub. Twentygauge sheet metal waschosen as a compromisebetween the 18 gaugefloor and the 24 gaugetub. Pieces 1-1/2” widewere bent into 90 degreeangles, 3/4” x 3/4”, using asheet metal bending brakeIf you don’t have a brake, a bench vise can be used as well.Cuts and notches made by tin snips allowed bending the flangealong the floor's contour.The flange was punched with holes every two to three inchesand spot welded to both the floor and the cheek.

Photo #33a & 33b: At the front of the band there will be a gapbetween the band, the passenger compartment floor, and therear quarter panel. A cardboard template was cut to fit the gap.The template was used to cut a patch panel out of a piece of 18gauge sheet metal. The metal was tack welded into place, thenwelded solid with a continuous bead. The edge of the patchalong the quarter panel will be sealed with autobody sealant, aswill the band.

Photo #34: Apedestal wasconstructed tosupport the trunkhinge box and tostrengthen the tub.The sides of thepedestal extend thewalls of the hingebox down to theband. Paper templates were used to create the four sides.The templates were transferred to 18 gauge sheet metal andthe pedestal sides were tack welded to both the hinge box andthe band.

Photo #35: The inner quarterpanel was then rebuilt. Thispanel consists mostly of flatsheet metal. Paper templateswere made and metal patcheswere cut out of 18 gauge sheetmetal. One of the templates isshown taped to the quarterpanel just above its patch.These patches were tackwelded into place on thequarter panel. Once tackwelded into place they couldbe adjusted, tack welded toeach other, and tack welded to the band. The patch at thepeak of the band was welded to the new baffle. The level offinish for these welds is a matter of personal preference. Thesewill be covered by upholstered side panels so perfect finishwork is not needed.

Photo #37: With thetrunk wall and innerquarter repaired,flanges should be madeto attach the front andrear edges of the bandto the floor. Shownhere is a papertemplate that was usedas guide to make thecuts and notches on the flange material. Holes were punched

Photo #36: The repair ofthe inner trunk wall wasmore complicated sincepatch panels are notavailable for sedan bodystyles. The end of thefourth bead was compro-mised by rust and had tobe cut away. We began by

fabricating this patch panel first. Starting with a piece of 18gauge sheet metal approximately 6 x 12 inches, we marked astraight line ending in a "T" to serve as a guide. Using the small1/4 inch die on a bead roller, we rolled a bead that ended atthe "T". With a straight bead established, we moved on tolarger dies, making the bead wider and deeper. Since most ofyou may not have a bead roller, this shape can also be formedwith a ball peen hammer and some elbow grease.The patch panel was then tack welded into place. The newbead ties in nicely to the original bead above it. The remainderof the trunk wall pieces were made by similar processes andthen welded into place. If you are working on a 2-doorhardtop or convertible, you can avoid making your ownpatches and use repair panels P/N 31-317 and 31-318 here.

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in the flanges and they were spot welded to the band and thefloor. With the tub tack welded in place, and all the flanges inplace, the tub was then welded with a continuous bead all theway around the trunk floor. We made sure to weld only inshort bursts to keep the heat down and to avoid warping theband or the cheek.

Photo #38: With the tub finishedwe then tackled the rearwheelhouse extension. Theextensions, P/N 31-89 and 31-90, are sturdy pieces of metaland they do take considerableabuse. The extension is also thelower stabilizing point for therear quarter panel, keeping thequarter panel from flexing andfatiguing. Simply welding theextension to the thin 24 gaugetub band without bracing ofsome kind wouldn’t have been stable enough. This would beespecially true if the band was not spot welded to the innerrear quarter and was held on only by sealant. We firstreinforced the extension by welding two pieces of 12 gaugesheet metal to the back side of the extension. These will notbe visible from most angles. The triangular reinforcementpiece is evident from the spot welds visible on the inboardunderside of this extension. A second piece of 12 gauge waswelded to the upper surface of the trailing edge where theextension would be welded to the inner surface of the rearquarter panel.

Photo #40: The seat backsupport was then modified to fitaround the new larger wheeltubs. I began by tracing the leftside of the support onto a pieceof corrugated paper. I cut outthe template which included theholes that marked the originalspot welds. The right side wastackled in a similar manner at thesame time.With the support templatepositioned by alignment toolsthrough the original spot weld holes, the template wastrimmed to fit nicely around the new wheel tub.

Photo #41: The template outlinewas then transferred to thesupport and the excess metalwas removed with a cut-off tool.Additional trimming wasnecessary to give the best fit ofthe support to the tub. Thesupport was then welded intoplace using the original spotweld holes in the package trayand along the rear of the floor.

Photo #39: A piece of 12 gaugeapproximately 3 x 4 inches insize was welded to the outboardsurface of the inner trunk wall.This piece reinforced the walland spread the load over a largerarea. Braces of 1/8 x 3/4 x 3/4angle were welded in placebetween the trunk wallreinforcement and the reinforcedportions of the extension. Thisbracing will keep the extensionin place, will prevent the rear

quarter panel from flexing, and will take the strain off the band.Be sure to mock up the gas tank filler tube to check clearancesbefore welding these braces in place. The right side wheel tubwas then constructed using techniques similar to those shownin the steps above. When the right side hinge box support wasremoved, the car lost the forward mounting bracket for theoriginal equipment jack. I have chosen to forgo the originaljack for a more compact modern jack that will be hiddenbehind custom trunk panels. For that reason the rear jackbracket on the trunk floor was also removed.

Photo #42a & 42b: Flanges weremade to fit along the vertical inboardside to the cheek as well as acrossthe top of the band. A piece of sheetmetal was added to the support tofill in the quarter circle shaped gapleft by the missing original innerwheel tub. This increase the flangelength and strength across the top ofthe band. As one can see by theamount of metal cut from this

support, modifica-tions will need tobe made to the rearseat bottom andbackrest frames,the seat upholstery,and to the sidepanel. With themetal workcomplete, a generous bead of autobody sealant along theunderside of the Pittsburgh seam and along the edges of theband will keep out the elements. The underside of the tubscan then be painted or undercoated for a finished appearance.The only question now is how wide do we want the new reartires to be? Good Luck.

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