Gale's Mk II (RCR)
- Thread starter Gale
- Start date
I've been working on an RCR MK II for about a year and I've run into a snag. I've done a suspension setup using the directions mostly based on the build manual from RCR's website and Tom's RCR trackracer. I've started to set the body and I've set the front body on the bobbins, moved the rockers as far back as possible and matched the front body piece. The wheels are well centered I think and I now have interference with the rockers when the wheel is turned back into the rockers. It's close and I think I can trim to get the clearance to turn more but when turning the wheel the other direction the tire hits the front part of the fender. In other words, I can't turn the steering wheel very far in either direction without interference from the fender openings.
Tires are Goodyear Blue Streaks like used on the originals. I don't understand what I've got happening. It looks right when comparing them to the originals but the tires seem to be to big to fit. Also, they aren't recessed under the fenders like the pictures of the race cars from day appear to be.
I know that this isn't the first project to have used the tires so I'm looking for help trying to figure out what I'm missing.
Gale
Tires are Goodyear Blue Streaks like used on the originals. I don't understand what I've got happening. It looks right when comparing them to the originals but the tires seem to be to big to fit. Also, they aren't recessed under the fenders like the pictures of the race cars from day appear to be.
I know that this isn't the first project to have used the tires so I'm looking for help trying to figure out what I'm missing.
Gale
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I think reducing the OD on your tire is the easiest solution. I’d think you need to stay around 25” on the fronts for a comfortable fit.
I have the mk1 body, which I believe is the same dimensionally in the areas you are referring to. My issue was compounded by have the front wheels widened to 9.5 which adds .5” to the outside. The only conclusion I came to is that the front and rear edges of the inner fender must be trimmed to accommodate. I had rcr “flare” my front fenders but that must be redone and widened to properly cover the 6.00 blue streaks and widened wheels
+1
Also, is the 'offset' of the wheels themselves different from 'stock'?
(Edit: I see the latter has already been asked!)
What size are your front tyres ??
Whatever equates to 215-60 R15 is pretty comfortable.
215-60 R15 is equivalent to 25.15" dia x 8.46"wide ( section width). Spains book states 5.5' on 15 for MKI ( 26" dia- Dunlops? ) and 9.75'' wide for MKII ( no dia specified-Goodyear). If you hunt around on other build threads Im sure this has been debated before on RCR stuff. As I mentioned earlier a stack up of parts dimensions that create the scrub radius increase. Somewhere I have a dwg of wheel offsets for Cobra vs GT40 that might be part of the problem.
Thank you all for the responses. The tire markings are 8.00-15 rears and 6.00-15 fronts. I've spent a bit of time on the problem today. The tread on the front tires is a bit over 9" and the measurement from side wall to side wall is 10.5". Dia is 24.25". Didn't measure the sidewall height. Don't know what the conversion number would be for the Goodyears. 225(235?)-60 R15 would be my guess.
I don't know it the offset on the wheel is different from the originals. They are the wheels as supplied by RCR. I had the rear wheels widened for the bigger tires that I intend to run but I didn't change the fronts. Front wheel bead width is 7.5 wide.
After looking at this I've come to the conclusion that the front tires will need to be narrower and lower profile than what I have there now. It works for clearing the fender wells and a narrower tire is going to be under the fenders rather than even with the outside of the fender. Either that or I will need to modify the from clip. I don't really want to do that.
This whole thing started with the wider rear wheels and matching the tire manufacturer for the fronts. The real down side to this of course is these tires where expensive and now looks like I won't be able to use them. rats....
As to "scrub radius", don't know enough to check and I wouldn't know how to rework the problem. Space between the suspension mountings and the outer edge of the fender is pretty tight.
Once I have this figured out then the next step is getting the rocker panels in the correct position so the I can start setting the body. I've read a lot about this process and I now are in the middle of it...I get it now. My head is starting to hurt.
Also I talked with Chris Kouba today. His insight was helpful and he gave me some measurements from his car that helped me understand a bit more of what I need to look for. Thank you Chris.
Gale
I don't know it the offset on the wheel is different from the originals. They are the wheels as supplied by RCR. I had the rear wheels widened for the bigger tires that I intend to run but I didn't change the fronts. Front wheel bead width is 7.5 wide.
After looking at this I've come to the conclusion that the front tires will need to be narrower and lower profile than what I have there now. It works for clearing the fender wells and a narrower tire is going to be under the fenders rather than even with the outside of the fender. Either that or I will need to modify the from clip. I don't really want to do that.
This whole thing started with the wider rear wheels and matching the tire manufacturer for the fronts. The real down side to this of course is these tires where expensive and now looks like I won't be able to use them. rats....
As to "scrub radius", don't know enough to check and I wouldn't know how to rework the problem. Space between the suspension mountings and the outer edge of the fender is pretty tight.
Once I have this figured out then the next step is getting the rocker panels in the correct position so the I can start setting the body. I've read a lot about this process and I now are in the middle of it...I get it now. My head is starting to hurt.
Also I talked with Chris Kouba today. His insight was helpful and he gave me some measurements from his car that helped me understand a bit more of what I need to look for. Thank you Chris.
Gale
Looking at the specs it is close to a 245-55 R15. The diameter is fine, the section with is what is getting you. They’re almost 2in wider than my fronts.
I don’t think they make a narrower G7 though.
Also, your front wheels look a lot more outboard than mine.
I don’t think they make a narrower G7 though.
Also, your front wheels look a lot more outboard than mine.
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Bill Kearley
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The answer is simple, you won't need to turn the steering wheel much, just a blip on the gas will get you around the corner. Also the spinner looks like it should be on a bit farther. check the front track as to what it should be. Scrub r is only the difference between theory and actual tracking with respect to toe out on turns and is not the issue, I think it's all in the tire size.
Scrub radius also affects the tire to sponson contact point which appears to be the problem Gale has. If for example, IF he was able to machine say 0.75" of hub face of wheel and set tire inboard the problem would be diminished (I am not suggesting he does that-just that might be a possible cure, obviously with considerable investigation before removing metal! ) Bills suggestion that spinner looks to be outboard has merit, check that wheel is snug against hub face and not riding up on drive pins etc. We have had a few members here lose a wheel from just that issue in the past. While Im thinkin about it, have you measured the actual length of wheel arch opening @ hub height on a proper MKII, maybe they are not same as MKI and since you appear to still have to fit the MKII scab's you could rectify if need at same time.
Bill Kearley
Supporter
That's all true, but i think something simple has been overlooked. If I was in my shop I'd check my tire size, rim offset / width and pass on. I have a MK1. I know the fender is different but is the wheel arch much different on a MK2 ?
Been a while so but have had to move the project because we lost our shop. With the move going on I haven't been able to work on the car. But I have done research to figure out what the problem is. Based on comment in the thread here I started looking at the Scrub radius Jac Mac suggested in particular the .75" hub face removal. Not something I'm going to do but it gave me insight. Turns out a couple of things are going on. The first thing I found was based on what Bill said. Check the rim offset. The wheels I have are about a half an inch wider on the outside than on the original race cars. Which factors in to and inch wider on the over all outside dimension. Add to that, as near as I can tell based on the info I've been able to gleen, the mating surfaces of the wheel and hub is about .375 per side to wide give or take a little. Added together that makes the outside dimension about 1.750 wider than a MKII we have racing here locally. We found a pair of 235-55 used tires and mounted them and they clear just fine on the body issue but are much to wide to fit under the fenders. The edge of the fender arches are the same as on the MK1 the difference being the fenders have a higher arch over the wheel. The body isn't as flat at the MkI. So now I have tires that will need to be replaced with something else as the Goodyears aren't going to work and I'm not going to mix tire brands front to rear. Question then is, will 215-55s to the job? The 55s don't fill up the wheel aches the way I'd like. I think that Avon has sizes that will work.
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Bill Kearley
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Howard Jones
Supporter
I have found that 245-40-17 is just about max in the front when mounted on a 8 inch wide wheel. By the way a 245-45-17 won't make it on my car. It's that close on my GTD.
Go on Tirerack.com and do some spec comparisons as it relates to tire dimensions. Start with any 245-40-17 specs and compare to your sizes.
Go on Tirerack.com and do some spec comparisons as it relates to tire dimensions. Start with any 245-40-17 specs and compare to your sizes.
I've been away for a while. My wife was sick and I needed to be with her. I'm getting started again on my builf and I'm looking for a source for a set of hinges for the rear body panel like the one in the picture. And in the other picture, thank you to Bill Hough for building some inner panels and ducking for me. Nice parts and he did them quickly.
Gale
Gale
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Is it just me or the fiberglass looks very poor quality ?
