This is a little post for those of you who may want to get maximum clearance in the bumpstop area for running those wide tires. What I'm looking to do is get my 17x11 rear wheels tucked in so it looks better. I have the 36mm offset rims and am currently using 1.25" wheel adapters for them to fit. If I use any smaller adapters/spacers, clearance issues will arise with the LCAs, rear bumpstops and the inner fender wall. The LCA issue has been solved by using square tubing LCAs, but this will address the inner fender wall and bumpstop area. In the first pic, the rear bumpstops were cut off, and my plan was to cut an "F" through the outer layer of the inner fender area, heat it with a torch, and hammer it flat, weld it back up. This however didn't work for me, as, in areas, the metal is 3 layers thick with space in between 2 of them. Now I see why people just cut a section out and weld in a flat piece, which is what I ended up doing. I will need to find a new spot for the bumpstop. I have seen a fourthgen with it relocated to above the LCA. As I stated earlier, there is no benefit of cutting that F shape in the panel as pictured.

Red - needs to be cut out and removed
Green - previous location of bumpstop
Blue - two layer thick sheetmetal
Yellow - possible location of a spot weld

notes: cut the red area as straight as you can as a new piece of sheetmetal will need to be cut to fit and welded, I used a 4.5" grinder with a cutting wheel.
- be careful to only cut through the outer layer of sheetmetal as you will be leaving the inner layer intact
- the area of blue lines is where you will cut through 2 layers, but leave the underlying 3rd layer intact
- this side had a spot weld going through all 3 layers and had to be drilled, but I don't remember encountering this on the other side

Outer layer of sheetmetal cut and removed.

I cut the areas in yellow so I can heat them up with a torch, hammer flat, and weld back up. The red x's are spots that I previously cut that is a little excessive... probably don't need to cut back that far. The green circles will need to be heated with a torch and hammered flat. The bottom pic is carboard cut for a template for the replacement sheetmetal.

New sheetmetal welded in. This is the passenger side which had already been completed, but just a mirror image of the driver's side pics posted above. On this side, I ground down the weld in the spots where maximum clearance was needed, painted and coated with 3M undercoating. Next up is going to be getting some ARP 3.25" wheel studs and some Skulte wheelcentric wheel spacers.

Nice job. I'll be doing this mod soon so this was a good read and bit of information.

Thx, it's obviously nothing really complicated or anything that's too hard to figure out as you go, but hopefully things like this give ppl the confidence to take on such projects, or like you, give a heads up on what to expect.

Trust me. it is nothing for me to worry about. if you look at some of the threads I have staretd that is nothing compaired to cutting out my factory sub frame and making new frame rails so I had room for 3" exhaust off the headers. Then I made custom SFC and a 4" single exhaust. It just gives me a heads up on what to expect. I also made a long tube T56 crossmember and have tons of ground clearance.

Anyway nice job.

can you post a pic of what lca your using, i need to get a set fto fit some 19X10 c6 rims i just got, then decide how how much clearence i have because i want to run 295's in the back

Just thought I'd mention a lot of people put bump stop bumpers on there shocks arter this mod do a search for more info. I'm going to do this at some point also nice pics and info.

Thx, 87tpi, I'll definately check those posts out. Sounds like it beats trying to weld something up to move the bumpstop to the LCA area. Godreject, I am using a set of Redline Performance Engineering Stage II LCAs. This pic is my clearance with .38" spacers on my particular setup.

thanks 4 the pic and info it will be helpfull since im instaling some C6 19X10 rims in the rear, i think i will purchase umi lca's and brackets and then figure out how much more cutting i will need to do, thanks

OMG!!! You know how long I have been looking for info on fitting 17" x 11" rims!

My difference though is...

My ROH Snypers are the direct fit 17" x 9", 3rd gen wheels. zero offset. And, I want to send them off to be widened to 17" x 11".

Now, if I am right....Think of your adapters as part of your wheels...You would have 6.92" backspacing? Correct?

I have 5" backspacing right now....I'm want to add 2", for 7" of backspacing. 6.92"....7"....Same thing.

So...It looks like I would hafta do the same thing to mine?

Why did you put a piece of metal back in the cut layer, instead of simply welding the 3rd layer to the 2nd layer? Would the lack of piece of metal really be that different, for a street car? I'm not drag or autocrossing my car, so would I really need that piece put back in?

What size tires did you put on those 11s?

I have 315/40s Goodyears on the back. The 17x11s are the low offset (36mm) ones which Skulte lists as 7.397" backspacing. Old setup would have been 7.397" - 1.25" (adapters) = 6.147" effective backspacing with no mods required, but they did stick out.
New setup should be 7.397" - .50" (Skulte slip-on spacers) = 6.897" effective backspacing, if I am correct, with the above mods done.
If you end up with 7" backspacing and we are doing our calculations and measurements correct, then the worst case scenario is that you should have to use a thin .100" spacer or so, if you do this bumpstop/inner fender mod. What I did was cut some spacers out of a truck mudflap (each was a thickness of .19"), drilled holes in them, and stacked them to see how thin of a spacer I could get away with after doing these mods. I came up with .38" of spacer gave me enough clearance, so I ordered some Skulte .50" spacers which should give me a little more wiggle room.

As far as welding that piece in.... there is really only two layers of sheetmetal back there. After cutting out the outer layer, that would leave only 1 layer for support. I figure that they had that outer layer 'ribbed' to provide additional support, so I am wary enough of just taking that ribbing out, and being a unibody car, I don't feel comfortable just leaving a big hole in that outer layer.

I cut the whole side of the frame rail off for my mini tub project and replaced it with a piece of 11 gauge running from the inner LCA mount thing all the way up and back to the rear of the wheel well. Plenty strong and no issues whatsoever with it. Im running 8.5" of back spacing and still have 3/4" or clearance after the tire is installed.
here it is, seal sealed and painted.


on your car, i wouldnt have just left a big open hole where you cut either, though its probably mose than enough support left, you need to put someting back in there or it will fill up with road debris and rot.

I read your minitub thread a while back, but realized as soon as I saw your 'in progress' pics that that was a pretty big bite I would have problem chewing. Especially after I read that you used 11 gauge sheetmetal. I like the idea and I bet you probably won't have a problem with support, but I would have been in a bit over my head. Love the coilovers!

hey iceman02 do you have any pics from the rear showing how well the tires tuck under? some before and afters would be real cool if you got it.

I did not have any pics as I still have not ordered my longer wheel studs, so she still sits on jackstands. But I did bolt up one wheel with the 1.25" adapter, took some pics, and then took those off and put on the .50" spacer.

Angle 2

I am going to put my rear 315's tires on soon. It looks like your rear tires are inline with your outer fenders? Could you have put it in more further inside? Would it make a different if there was a different LCA with round or circle bar arms instead of a square box bar arms and would the the wheel be more inside the fenders?

I am interesting to know.

Looks like a nice job you did.

Thank.

Yea, they are pretty much inline with the fender. Actually one is in a little bit further than the other, even though I'm at stock ride height. I can't say whether or not a tubular LCA would give more clearance than the ones I bought, but maybe just a little. I'm going out of town for the week, but I will post some more pics now that I have my spacers and longer ARP wheel studs installed. I'll also do a little how-to on installing the ARP studs. Those of us who have 4 wheel disc brakes either need to pull the axles or drill holes in the plate that the brakes mount to (which I did) in order to get those long studs installed. I also need to do some more 'massaging' of my fenderwell do avoid contact with my tires when the suspension is compressed.

Thanks for letting me know. Looking forward to your more pictures post up.

Replacing factory length studs is possible without modification (4 wheel disc). As such, you can remove the factory studs with just a big hammer.... there is plenty of room behind the hub for removal, but for longer stud replacement, either pulling the axles is required or it is time for improvisation. I didn't want to pull the axles, so here is what I did. I drilled a hole big enough to fit the head of the wheel studs through in the plate that the brake calipers mount to (behind the axle hub). First, I pounded out the old studs, then I drilled a hole through that back plate (going through one of the stud holes in the axle hub). Next, I used an 90* battery powered drill with a unibit (coming from the backside) to open it up to the desired diameter. Then I pulled the studs through the hub with an impact.

thats some good thinking. I dont know if it would have worked with you backing plate setup, but im running ls1 brakes, and if you unbolt the caliper bracket, it will move out of the way enough to wiggle a longer stud in.

You mean, unbolting that backing plate from the axle itself? I thought about trying that, but noticed that the backing plate can only move outward once it is unbolted. So you're saying that there may be enough room if you unbolt it and tilt it a bit. That would probably beat drilling a hole in it like I did if it would work.

I was cutting a car up for scrap and thought this pic might be usefull to anybody considering doing this as it shows the layers of metal and howmuch suport is there or how much you would be taking out.

yeah, i meant backing plate, brain fart.

Now that im thinking about it again, the ls1 backing plate has a small 3/8 or 1/2" deep recess in one spot, so, once the backing plate was unbolted, i was able to line that recess up with the hole in the axle flange and wiggle a longer stud in.

I will see if i can find a pic.

As for the previous post with the cutaway pic, that will show why i opted for 11 ga. There is a LOT of metal in the bump stop, al least 3 pieces of heavy steel all spot welded together.

Im just gonna revive this thread instead of starting a new one....

I cant find those threads about the bumpstops.... After you remove the stock ones, what do you do about them? I couldnt find any info on mounting them on the strut.

I did a quick search and found this post the 4th one down mentions it. http://www.thirdgen.org/techboard/su...shock+bumpstop (Lowered cars & rear bump stop)
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sorry link did't work. I bumbed the post to the top it said something about lowered car and bumpstop in the title.

link worked ok! Thanks for the info.

I guess you used better search words than me. I look for 3 days and couldnt find anything useful .

Not sure why you guys are doing bump stop mods and such for 17x11's...

I have 17x11 gran sports (black ZR1's) on the back of my '91 Formula with the +50mm offset. I used a 1.25" bolt-on spacer with a stock 3rd gen rearend and they tuck in VERY nicely... actually almost too much. LOL I have the stock bumpstops and everything. Only thing I did was barely clearanced the fenderwell on the front lower portion... that's it. The car is also lowered with the Eibach pro-kit.

I though I was the only one! I'm running 19x11s (295 tires) on the back with no issues...well a little of the bfh on the inside, and when I painted the car I cut off the fender lip. Mine tuck nicely...and I'm lower than you!

that is the most useful pic ive ever seen on this forum.

i have 17X11 ZR1s with adapters on my 91 camaro (315x35x17) and and they fit without any problem and the bumpstops are almost tucked inside the rim.

i need to raise my car up a little which will cause the bumpstop to hit the rim. therefore i need to do the bumpstop mod mentioned above. (awsome and much needed by the way)

Simon in AZ

Pretend your adapters are part of the wheels....What backspacing do you have then? 5.9"?

I'm running 17x11 (50mm offset) with a 315/35/17" and a 1.25" bolt-on spacers.... if I added the spacer to the wheel my backspace is about 6.5-6.75"

1/4" is a big range to talk about, for this.....Are you saying WITHOUT the adapter, you'd be at 6.75"-7"? That would require some big wheel well mods. I think +-6" is the max you can go, until the wheel touches the wheel well.

BUT.......My question was for BatSipJet anyways, since he says his fit with zero wheel well mods, and the BFH (at the very least) has to be used.

i was wondering what did you do with your inner fender lip.... did you roll it in?
im having trouble with my c6 z06 wheels in the back, they rub.... if i hit a dip on the road they rub.... and i cant lower the car unless i roll the inner fender lip...

1/4" isn't much at all... I was only saying that because I was calculating these numbers and didn't go remove a wheel from my car and measure it.

You need to recheck your math... if I said my BS was 6.5-6.75" WITH the spacer then WITHOUT it the BS would be 7.75-8.0.

**17x11 ZR1's with 50mm offset are about 7.93" BS, subtract my 1.25" spacer from that and you'd get 6.68" BS (6.5-6.75" I mentioned earlier)

You can run about 5.85" BS on the stock rear... I know this for a fact because I used to run a stock rear on my GTA with 15x8 draglites and 5.5" BS... they tucked up VERY well.


Here is some good info... make sure and scroll all the way down for recommendations.
http://www.skulte.com/adapterfaq.html

As for a BFH on my car... it was VERY little and only at the bottom front of the wheelwell. If my car wasn't lowered I don't even think this would be a problem.

You know....I give up...I ****ING give up on trying figure out everyone's adapter crap...FWD fitting-style Corvette wheel crap....

I deal with wheels that FIT. Not crap that requires double the lugs, double the lug nuts

I got wheels that FIT. No extra BS required.

I'm not directing this at anyone in particular...Just venting...Just pissed of trying to figure all this crap out, before I send my Snypers off to be widened.

Its really not difficult at all man... what size are your snypers? How do they fit right now? If they are 8" or 9" wide, you could have them widened 2" more and make them 10" or 11"... then probably just get a 1" or 2" spacer and make them work just fine. Its really not that difficult.

well its kinda dark outside... i went out and measured the adapters and they are 1.5". And there is still another 6" until the end of the rim. I have drums on the back so i have no idea if that makes a difference or not. I measured from the back end of the rim to the adapter and there is 6" of space.





hope that helps.

pictures are easy to take so let me know.

Simon in AZ

My Snypers are 17" x 9", 4.5" bs. Wideneing 2" will give me 6.5" bs. Which, I think is pretty much the MAX you can do, with just a BFH. Plan is to get 315s.

I'll use a BFH....That doesn't bother me. Nor does trimming the inner lip.

But using spacers isn't much better than using adapters. That would depend on how long the stock lugs are anyways. I tried that on my 97 Tahoe years ago, and the lugs were too short to use the spacers.

That's pretty much what mine looks like... the inside of my rim is barely hanging over the bumpstop and my sidewall is about 1/2" from the LCA. I'm assuming those are 50mm offset rims? If so the only real difference is I'm running a 1.25" spacer and you have a 1.50" spacer.

Fresh paint? Looks nice!

You'll be fine with that and a BFH... that's essentially what mine is taking the spacer into account.

EDIT
-Better yet, just go out and see if you have 2 more inches of clearance going inward, that will for sure tell you.

anyone with pictures of where they are moving their bumpstops too?

I am going into the shop tomorrow to see what we can come up with.

That's my whole point of replying to this thread... just leave them alone. From your pics mine are the same way. I've put over 20k miles on mine this past year with no issues. The only problem is that if you put your car on a chassis lift and the suspension hangs down that the wheel/sidewall will hit the bumpstop. Not a huge deal really...

Now I did completely remove my bumpstops and mounts on my '91 GTA... cut it all out, smoothed it, welded it up, etc. But then again I'm running 28x13.50 slicks on that car. Definitely needed some extra clearance on that one.

*I also forgot to mention that the reason I don't have issues on my '91 Formula is b/c its lowered which means the rim rides high and above the bumpstop. If your car is stock height, then the rim rides lower... possibly interfering with the bumpstop. Was that the whole point of the original post?

i am trying to lift the a$$ of the car up with some Moog CC635s. and when i tried to put the wheels back on, the bumpstop does hit the wheel like you say. if i was to lower the car down from the chassis lift, would that lower it back under so the wheel will fit but not hit the top of the rim when i drive? that is my fear.

the way the car sits now they ride great and i have no problems at all. its just when i put my new coils in i have this fear that it would slam into the to of the rim.

Simon in AZ

Yeah, sounds like you might run into some problems with interference if you raise/lift the car up higher. Like I said... I guess that was the whole point of this topic.