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The VIPER Garage  |  How To Instructions  |  How-to section  |  Opening up Rear Wheelwells for Big tires
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Author Topic: Opening up Rear Wheelwells for Big tires  (Read 1841 times)
RTTTTed
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Viper Nation - ezine
« on: August 10, 2015, 11:40:41 PM »

With my Tranzilla and GForce racing T56 transmissions 5th gear is upgraded to .89 and 6th gear to .75.  With the lower transmission gears the engine stays in it's rpm range and therefor runs much faster after 140mph.  Unfortunately, this lowers the top speed to 196mph with stock (26" tall tires) and only 215mph for 28" tall tires.  233mph is the top speed for 30" tires.

Also unfortunate is that Gen 2s are designed for 26" tires.  28" drag slicks will rub and Sheldon's M/T Drag Radials wore through his plastic inner fenderwell. 

Because I need the high speed for runng Land Speed Racing I will cut and modify my frame and reshape the inner fenders at the front.  To run 30" tall tires I am expecting to cut and weld the frame crossmember at the lower front of the wheel tub to remove 1".   The center of the tire is above the lower frame crossmember that I need to cut, but when jacked up the tires will hit so modification will be required.

The attached pics show the interference even while the tire is hanging in the air while the car is on jack stands. ...  Firewall behind seat needs to be moved forward in the middle and the frame crossmember that need to be narrowed at the front bottom is also an interference.
« Last Edit: August 21, 2015, 12:24:47 AM by RTTTTed » Logged
1999 1200rwhp TT GTS - ART, 2001 Roe sc GTS- (4 sale), 440 Duster restomod (sold), 3x Stealth TTs, 92 Daytona IROC with T3, 580whp/1080wtq Cummins pickup.
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Viper Nation - ezine
« Reply #1 on: August 21, 2015, 12:32:36 AM »

First I place the Viper on blocks and removed the wheels, then the inner wheel tubs.  The 'push pins' expand when the center pin is pushed into the body so removing them is easy when you have the right tool.  I used this screwdriver shaped tool. in the picture, to lift out the pins and the pry the body out of the holes. 

There are 3 'special' rivets holding the quarterpanel to the support structure with the inner wheelwell sandwhiched in the middle.  Drill the rivet heads to remove them.  The back of the innerfenderwell is attached at the rear with 3 bottles to the battery cover.  Because welding is required, also remove the plastic battery cover - you'll need to disconnect the battery before doing any welding.

Now it's time to wrestle out the plastic inner tub and set it off to the side. 
« Last Edit: August 21, 2015, 11:17:56 PM by RTTTTed » Logged
1999 1200rwhp TT GTS - ART, 2001 Roe sc GTS- (4 sale), 440 Duster restomod (sold), 3x Stealth TTs, 92 Daytona IROC with T3, 580whp/1080wtq Cummins pickup.
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« Reply #2 on: August 21, 2015, 12:44:59 AM »

The rear cabin firewall is built according to the seat back angle and not the shape of the tires.  This metal structure is one of the features that the 28" tires rub on.  Both my 14.5 x 28 Hoosier Quick Time Pros and my 14 x 28" Hoosier R6 tires rub in this area.  The other area they rub is the frame crossmember at the bottom front of the inner wheelwell.  See first attached pic of inner wheelwell rub marks.

I found that when I drew a line down the middle of the firewall interference (toward the outside of the car) then used a dull cold chisel to create a dent line as a "prefold" all that was needed to reshape that structure to conform to the tire shape was a large 'Chevy Hammer" and some elbow grease to beat the firewall corner until the "prefold line" became a fold and the firewall was reshaped by hitting with a small sledgehammer until it was round matching the curve of the tire.  Note that the first pics are the Passenger side while the last pic is of the driver's side ww.
« Last Edit: August 21, 2015, 12:56:42 AM by RTTTTed » Logged
1999 1200rwhp TT GTS - ART, 2001 Roe sc GTS- (4 sale), 440 Duster restomod (sold), 3x Stealth TTs, 92 Daytona IROC with T3, 580whp/1080wtq Cummins pickup.
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Viper Nation - ezine
« Reply #3 on: August 21, 2015, 01:16:41 AM »

The next two pieces I need to modify are the front lower crossmember and the upright brace.  The upright is a support and the weld to the top of the crossmember needs to be cut though, preferibly by a 3" cutoff disc.  The thin sheetmetal welded to the support can be trimmed or the welds ground off and the lower outer support gussett merely cut that weld as well.  Using the hammer tap the 1" x 2" support forward out of the way.  We will reweld this into place after cutting and rewelding the crossmember.  0159 shows how I cut the support 'beam's' weld with a hacksaw to separate it from the crossmember.

I used a Sawzall and an airpowered 3" cutoff disc to cut nearly 1.5" from the crossmember lengthwise.  I cut along the rollcage's main hoop support plate.  I will weld the support plate to the crossmember making it a part of the car's frame for extra strength.  Once all the welds have been cut, the support beam pushed back out of the way and the crossmember cut ... I cut a piece of .060" thick steel to fit inside the now open crossmember to restore the frame and structure strength. 

I welded the support beam back into place, did some clean up grinding and painted the area well.  I wirebrushed and wiped the welding smudge then primered the area.  I covered the primer with some wheel epoxy paint I had and then shot some black over it so it'll look good.
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1999 1200rwhp TT GTS - ART, 2001 Roe sc GTS- (4 sale), 440 Duster restomod (sold), 3x Stealth TTs, 92 Daytona IROC with T3, 580whp/1080wtq Cummins pickup.
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« Reply #4 on: August 21, 2015, 01:25:36 AM »

The plate I welded into the modified crossmember is extended to fill the entire front crossmember for added strength.  I also used a thicker metal plate to add strength because narrowing the tubing weakened it.  I used .120" plate

I also welded the rollbar support plate to the crossmember as well, shown in second image.

Thanks to a suggestion by Joel Fortin on another modification we did, I had purchased some 1/4" Rivnuts on my bench and I installed those to replace the rivets for a neater, more secure job.  The rivnuts affix into the support structure behind the quarterpanels.  I used one rivnut at the outside front of the wheelwells.  If you damage your pushpins their holes could be drilled out and the pushpins replaced with 1/4" bolts into frame mounted Rivnuts. 

I drilled the inner support structure to install a rivnut that would bolt the quarter panel lip the the support structure.  Stupid fiberglass won't allow the rivnut to grip.  I am using JB weld epoxy to glue the rivnut into the support structure.  I installed a Rivnut nto the front lower corner of the plastic wheel tub.  That worked well. 
« Last Edit: August 21, 2015, 11:30:58 PM by RTTTTed » Logged
1999 1200rwhp TT GTS - ART, 2001 Roe sc GTS- (4 sale), 440 Duster restomod (sold), 3x Stealth TTs, 92 Daytona IROC with T3, 580whp/1080wtq Cummins pickup.
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« Reply #5 on: August 21, 2015, 11:36:38 PM »

I reinstalled the 28" slick and there is more than 1.5" of clearance from the tire to the frame crossmember. 

I reshaped the firewall, cut the crossmember and moved the support 'beam' on the other side wheelwell.  After welding a strengthening plate into the crossmember and spraying paint over the bare metal, both sides are modified. 

« Last Edit: August 30, 2015, 02:04:25 PM by RTTTTed » Logged
1999 1200rwhp TT GTS - ART, 2001 Roe sc GTS- (4 sale), 440 Duster restomod (sold), 3x Stealth TTs, 92 Daytona IROC with T3, 580whp/1080wtq Cummins pickup.
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« Reply #6 on: August 30, 2015, 02:15:00 PM »

I tried to insert a Rivnut into the fiberglass quarterpanel support along the wheel lip, but the fiberglass crumbled and wouldn`t hold the Rivnut.  I epoxied the Rivnut into the support panel.  I will use short 1/4`bolts with the threads coated with a never-seize compound. 

I also inserted a rivnut into the front leading edge of the wheeltub (instead of using a rivet). 

Reshaping the plastic wheeltubs using pressure and a heat gun is next and reattaching them inside the wheelwells.  I then used my 28 in slicks to wrap the wheeeltubs around and rope to pressure the areas that I wanted flattened.  I aimed a forced air heater at the wheeltubs and watched the tub carefully.  It did reshape nicely although a little slowly.

I mixed up an epoxy to fill in the quarter panel wheel lip attachment holes so that I could drill the holes in the fiberglass support structure where the quarter panel lip rivets through the inner wheel tub.  Filling the support hole, then using a 1/4" tap to put machine threads gets rid of the need to use Rivets completely.  Painting bolt heads and washers black hides the small bolt heads.  Poperly sized countersunk phillips machine screws will replace the 1/4" bolts eventually.  Specialty bolts require time to order. 

« Last Edit: September 19, 2015, 11:51:39 AM by RTTTTed » Logged
1999 1200rwhp TT GTS - ART, 2001 Roe sc GTS- (4 sale), 440 Duster restomod (sold), 3x Stealth TTs, 92 Daytona IROC with T3, 580whp/1080wtq Cummins pickup.
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« Reply #7 on: August 31, 2015, 09:18:08 AM »

To finish reshaping I reinstalled the wheeltub and the 28`tall slick then used 2 x 4`s and the heat gun to flatten the tubs in the are of the tire tread.  Once supported the wheeltub reshaped in a couple hours.  I`ll install a rivnut into the crossmember just outside the footprint of the tire to hold the tub away from the tire.  I also installed rivnuts into the frame to hold the wheeltub more securely.
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1999 1200rwhp TT GTS - ART, 2001 Roe sc GTS- (4 sale), 440 Duster restomod (sold), 3x Stealth TTs, 92 Daytona IROC with T3, 580whp/1080wtq Cummins pickup.
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« Reply #8 on: February 22, 2016, 11:00:51 PM »

I cut the upgright brace and the side gusset platem the the front lower frame rail crossmember for tireclearance on my Roe Supercharged 2001 GTS.  This is  a street car but with the Tranzilla T56 tranzmission my new highest speed with stock tires is 196mph and without Nitrous Oxide I should already be faster than that in the mile.  With 27.6" tires my top speed will be about 215mph and I will be able to bolt my wrinkle slicks on this car as well.  My 16" x 28" wrinkle slicks,

I took a heavy hammer and bent the firewall at the front of the wheelwell into a curve to match the tires and to keep them from rubbing on the plastic wheeltubs.

I cut the frame crossmember back about 8" and then tapered that to the a zero cut.  I removed about 1in. of the 2.3" .070" steel.  I cut a piece of .120" wall flat bar to 2.75 x 10" and bent that to fit then welded that into the side of the crossmember.

I cleaned the area and ground any bumps in the weld (stress risers) then primered the area.  After a final check I painted it with acrylic enamel.




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1999 1200rwhp TT GTS - ART, 2001 Roe sc GTS- (4 sale), 440 Duster restomod (sold), 3x Stealth TTs, 92 Daytona IROC with T3, 580whp/1080wtq Cummins pickup.
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« Reply #9 on: February 22, 2016, 11:33:53 PM »

Again I used my heat gun to heat the plastic tub then put the heavy flat rotor on top of the curve on the floor to straighten the curves out of the inner plastic tub.  The front bottom edge of the Tub now needs to be flat and more than an inch forwad of where it was curved before.

I also heated the 'kink on the forward portion of the tub to make that flatter now that the firewall has been bent out of the way.
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1999 1200rwhp TT GTS - ART, 2001 Roe sc GTS- (4 sale), 440 Duster restomod (sold), 3x Stealth TTs, 92 Daytona IROC with T3, 580whp/1080wtq Cummins pickup.
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« Reply #10 on: September 17, 2016, 10:37:59 PM »

After reshaping the rear wheelwells 355 x 30" x 19" Pirelli tires (27" tall) fit easily on the back of both my Viper GTSs.  I have 2" clearance from tire to wheel tubs

I ran my Hoosier 14.5 x 16 x 28" Hoosier wrinkle slicks and they no longer touch the inner plastic tubs.  I can fit a 2x4" between tire and wheel tubs which is 1.5" clearance.

My new 325 x 50 x 15" Mickey Thompson ET Street 'R' tires are 28.3" tall and again, a 2 x 4" flat will fit between the tire and wheeltubs/

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1999 1200rwhp TT GTS - ART, 2001 Roe sc GTS- (4 sale), 440 Duster restomod (sold), 3x Stealth TTs, 92 Daytona IROC with T3, 580whp/1080wtq Cummins pickup.
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« Reply #11 on: March 20, 2018, 01:27:29 PM »

Now I'm finishing up the wheel well mods on my 1998 Hennessey TT.  This car has a dated SVS Twin turbo system that dyno shows 900whp.  Traction is an issue.  Best way to gain traction is taller and softer compound tires.  Stock gen 2 wheel wells only allow up to about 27" tall tires before rubbing through the plastic tubs and rubbing metal firewall of metal frame. So ...  here we go again.

Pic show starting the 'fold' to curve the firewall from flat to round for tire clearance.

2nd pic shows firewall folded, reshaped to the curve and frame cross member cut and welded narrower using .120" steel plate instead of .072" frame material and capping open end.

3rd pic shows finished wheel tub reshaped.

4th pic shows flattened plastic wheel tub Rivnutted/bolted back into place
« Last Edit: March 20, 2018, 01:32:52 PM by RTTTTed » Logged
1999 1200rwhp TT GTS - ART, 2001 Roe sc GTS- (4 sale), 440 Duster restomod (sold), 3x Stealth TTs, 92 Daytona IROC with T3, 580whp/1080wtq Cummins pickup.
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