firstgear

SRIII/63swc how much clearance is needed between the tires and the rear inner fender wheel well lip when set at proper alignment specifications to allow travel etc and not wipe the fender out?

John McGraw

Herb,

The lip is not the issue on midyears. It is the inside of the quarter about an inch to an inch and a half up where the interference usually occurs. To really figure out how much clearance will be enough, Figure out how much suspension compression will be your max, and then measure up that much from your existing at-rest tire location.Plumb down from that height on the inside of the quarter, and you will end up with the clearance to the lip that must be maintained to assure that the tire does not contact the inner surface of the quarter at full compression.

There are a lot of variables that you did not define that can alter the needed clearance. If you are using a stock suspension, or even a C4 suspension, 1/2" lip clearance is usually about enough, since both these suspensions experience pretty dramatic negative camber gain under compression, which will swing the top of the tire in and make more clearance. If you are using a C5-C6 rear suspension, running really tall tires, or riding lower than stock, you will need an inch or more of clearance to the lips. My convertible runs 17" tires with a C4 rear suspension, and 1/2" clearance has worked well on it, and the tires have only lightly kissed the inside of the quarters a couple of times in 5 years. My coupe runs 345 X 20 tires and has a C5/C6 rear suspension, and I am at about 1.25", and I think that is about as low as I can live with. The C5/C6 rear suspension has much less camber gain under compression, so you need to build in more clearance. Also the huge tires stick up in the wheelwells more, and this is further aggravated by a low ride height.

Short answer is: take the spring off of your rear spindle and run the spindle through it's entire range of movement, and note the closest place to the quarter, and use that as your benchmark to work from. If you maintain 1/4"-3/8" of clearance at the closest place, you should be golden.

Nothing worse than ordering a custom set of wheels and finding out later that they rub under compression, don't ask me how I know!



Regards, John McGraw

firstgear

somewhere my communication with Mike got off track. I had gotten my frame back in 2008 and when the economy dropped to its knees I stopped spending all money. By the time it started picking back up I was offered an opportunity to run a recent acquisition in Michigan.....that put the car on ice for over 3 years....so I am now just getting back going.

The suspension settings were way out of whack and I was concerned about the rear tires taking out the quarter panels. So I took the car to a friends shop and had them set all the suspension pieces at proper position.

The rear tire on the drivers side rubs inner lip and the passenger side has barely 1/8 inch.

I recall exchanging details with him about tire/wheel size and the necessary specifications. I even sent him the wheels and tires so all would be good. I was hoping that the wheels/tires would not be an issue as I too have had to purchase new tires/wheels for my '60 to get clearance and fit correct.....I hate spending again on something I already spent! GRRRRRR

So I was hoping that I could clip the inner lip and re-enforce the quarter with carbon fiber.

I have a set of GTS quarters in the basement, still in the box from when they first arrived over 7 years ago.....so I could use those but then that means I will have to probably get wider tires and wheels to make them look correct....of course I bought cheap wheels.....Billet Specialties...UGH!

John McGraw

Herb,

I have the GTS quarters on my coupe, but have stock quarters on my convertible. What rear suspension did you use on yours? If you used the C4 suspension, you can just section the strut arms and halfshafts to narrow the track width. My 59 and my 65 convertible both have narrowed C4 rear suspension on them, and you can make the suspension fit the car. On a C5/C6 rear suspension, you are what you are, and there is no way to narrow the track width after the frame is fabricated.

I made the mistake of buying a full set of ZR1 wheels for the coupe, without having the suspension mocked up, and I now have a brand new set of wheels sitting out in the shed! While they did fit and clear the lips, as soon as the suspension compressed 1.5", the sidewall of the tires rubbed on the inside of the quarters. I ordered a custom set of Budnik wheels, and the first set came in made to the wrong specs, so they had to go back to be cut apart and re-fabricated. I will never, ever again order wheels until I have the suspension completely installed under the car, body on the chassis, camber set, and plumb lines dropped to the floor from all critical suspension points, with the suspension at full drop and full compression. Just too many moving parts to do it any other way.

The silly damn thing is that I had plenty of wheelwell to use, as I originally built the tubs sized to accept 375 tires, but when I decided not to put the LSA drivetrain in the car, I dropped back to 345 tires. There was plenty of room to move the tires inboard, but I just did not want it to look goofy with a bunch of gap at the quarter. I just lost sight of the fact that the quarter starts curving inward almost as soon as it leaves the lip.!

If you went C4, it is easy to change the track width, but if you went with C5, you will probably either have to buy new wheels, or put on the GTS quarters.


Regards, John McGraw

firstgear

C4 rear......so it sounds like that is good except for the hassle.....my half shafts are carbon fiber so that may be a problem.....

John McGraw

What year C4? Not all C4 rear ends are created equal. After 1987, the rears got wider by about 3/4" (if memory serves me right), to accommodate the ABS reluctor ring. Early rears can fit under a stock set of C2 quarters, but post-87 rears usually have to be shortened. I believe that I shortened my 96 Dana 44 1" per side.

I just sliced the strut rods and sectioned 1" out of each of them and TIG welded them back together. The stock halfshafts I sent out to a driveshaft shop to have them shortened. I then ground the welds smooth and polished the shafts and ran them back through the balancing machine at the driveshaft shop to assure that I had not changed the balance with the grinding and polishing.

Even with the shortening, the wheels will need to be a wheel similar to a C5 front wheel, as the wheels can not have a deep dish to them. A lot of people find this lack of dish to be ugly, but if you put the GTS quarters on, you can add some offset to the wheels to get a deeper dish. The C5 offset look never bothered me, so I kept the stock quarters on my convertible. You can not shorten the rear enough to allow deep dish wheels, as this will make for a rear suspension that changes camber way to much during the up and down movement, and will make for poor handling.

An early set of spindle supports may be all you need to get back on track. These should give you 3/8" more clearance on each side. The halfshafts are exactly the same length if I remember correctly, the difference in width is all in the spindle supports.



Regards, John McGraw

Poorhousenext

Herb,

I'm a user of what I call "Fuzzy Logic" when looking at problems. If I'm reading correctly what you disclosed, then looking at John reply about what wheel/tire clearance he has had to use to prevent problem you have, my conclusion "Fuzzy Logic" wise is, Mike at SRIII built the frame set up to use the rear tire size and wheels you have with the GTS 1 1/2" flared quarter panels you purchased 7 years ago when you ordered your frame.

Times hasn't changed, but I'm reading with my "Fuzzy Logic" is you have changed your mind build wise, and now prefer to leave the body stock, an I can understand that.

So what is it tire and wheel size you want to use and what ride height relationship do you want top of tire to have in relation to wheel wells opening, because My "Fuzzy Logic" is telling me you want top of tire to sit looks wise, either with tire's top sitting at least level with top of wheel well opening or maybe up inside wheel well for more of a slammed look than stock wheels and tires from the day had. Is either one of those the case now?

Below are a couple of things that have changed with tires used back then and tires we are using to day.

Look at any picture of C2 with stock tires that came on it and ride height they were set at. Remember the wheel well's opening was designed around a 27" + .05 radius tire. The stock tires design Vs today tires we want to use are not the same.

Old tires have more of a rounded sidewall, where tire is fat in middle and tapers in at top. Today's tires have more of a square side wall, with little are no taper inward at top. Once you look at that along with how suspension moves as it collapses you should be able to visualize that if you used a 27.0 dia " with body set at same ride height, the late model tire would hit the inner side of panel before the old style tire would just because of profile design change.

Now what size tire diameter and what rim width are you wanting to use? The wider the footprint of the tire is the smaller the dia of the tire will be to prevent tire flex, so a taller tire that will be closer to original tire's dia and wheel well opening design but will have a narrower foot print. Short and Fat or Tall and Slim.

Another thing you have realized, that some haven't here, is it's not the center of the 1/4 panels width that controls how wide a tire you can use, it's that curve in panel and were tire's outer dia will come in contact that controls that. Seem some people think they have more tire to panel clearance if a GTS 1/4 panel is ill fitting as it's pulled away from body. Yeah, but not at front, that is unless they toe the tire inward to get same distance between front and rear of tire and panel. Never mind there is less clearance between front of tire and body now and poor tire wear as well as handling...

So if you want to use a larger than 27.0 + .05 Dia tire late model tire you will have less clearance between wheel lip as well as inner panel and tire as dia changes. So again when SRIII set up suspension he might have taken the dia of tires you had mounted into consideration and if they were a smaller dia than stock he just may have taken that into consideration so and had the axles made to move tire outward more so there was less gap between them and rear panel than if he had not. Again I think that is what you wanted.

Now if you want the rear tires to fit up inside body for s slammed look you are creating even more of a problem unless you are willing to modify the 1 1/2 inch flared fender's blister radius to provide needed clearance to do that.

Also get the impression you are wanting to moved to a larger dia tire and give up some footprint width so tires don't have as much of a rubber band look to them.

So what did you start with tire/wheel size wise and what is the body and tire "Look" you want "Now"? Are you trapped because of the axles or can a compromise be found so you don't have to reinvent the wheel(s), pun intended.

firstgear

I wasnt planning on the GTS fenders to begin with. I had bought them in anticipation but that wasnt factored in when I talked with Mike at the beginning.

I talked with Mike today and we had a great discussion. We talked over the problem and he said that 63 bodies can be all over the place size wise. So while it happens.....and it happened here we talked about options.

First let me say that I bought the GTS fenders before I even had the frame never mind the car. I had decided that I wasnt going to use them. I discussed this as an option with Mike to put these on and we both agreed that the wheels/tires that I had would be swimming in the fender well. I am trying to not but tires and wheels again......

One option that I have is to give the tire/wheel a bit of a negative camber. I will call the shop tomorrow and find out what they did with the back wheels. In a perfect world they put in 0 degrees, that would give me -0.5 degrees to -1 degree to put in. -1 degree should move the top of the tire near the wheel well .4 inches....which would be more than enough.

So I have some options here as well......

Also having the C4 rear end I may be in luck by the way it arcs in its movement...when it goes up it also goes in since it arcs in its movement.....I need to get the car jacked up in such a way I can get the movement of the wheel to go full arc and see where it hits.....so stay tuned to camber adjustments as well as checking tire/wheel movement.

This wont be happening this week as Sharon and I are headed to Hawaii for a cruise around the islands and then to Vancouver....11 days in total. Went all out this time and got a Royal Suite since my daughter , her husband and my grandkids will also be coming along and felt that the suite would be good place at times for the kids to come play.....

So I will be back by the end of the month.....stay tuned....

firstgear

talked to the shop and they try to hit right on the spec which was given as -.5 degrees.....but the range for the setting was listed as another 1 degree either way.

I ran some calculations on the impact of more camber, for every 1 degree it moves that upper area by the where the tire rubs the lip, 0.4 inches.

so it appears that I have more room to move.....now to check the upper area where the top of the tire might impact the fender.....

MatthewMiller

Oops, posted in the wrong thread.

firstgear

firstgear