First Generation Firebird

Tire Rubbing Issue 68 Firebird

Posted By: Kims68Firebird

Tire Rubbing Issue 68 Firebird - 02/20/19 03:29 AM

Hey everyone,
I own a 68 Firebird that has been a constant hassle during the 12 years I have owned it but it is MY Bird.
Long story short, this car has broken down on me so many times I can't count but I am finally on the home stretch of getting it to behave.

I took the advice of many car parts dealers who told me what Torq Thrust II wheels to buy for it and though I now have my dream wheels, they are a nightmare because I can't even drive it with any passengers because it rubs the front fenders on every bump or corner. Here is my setup- recently done (2-3 years ago) drum to disk front conversion with tubular a arms, just replaced cut springs to stock ride height springs hoping that would help- it didn't, kyb shocks in front are maybe 6 years old, no front sway bar because the stock one didn't seem to fit after conversion, gabriel hijackers on rear (drums) possible drop spindles on front? (Not sure, I believe they came with the conversion set but not positive if they were put on) new body mounts, front tires are 215s, wheels are https://www.jegs.com/i/American-Racing/286/VN6155761/10002/-1. Please help. Husband is "suggesting" that I should sell the money pit because he may or may not be upset that he can't ride in it! smile Won't happen though!

I had 15x7 K18 Camaro Rally's with the same tires on before these wheels that never rubbed even with the cut springs so I don't understand it.

Please help! smile
Posted By: Firebob

Re: Tire Rubbing Issue 68 Firebird - 02/20/19 03:55 AM

Where, on the fenders or body, do the tires tub? Front only? Front and back?
Posted By: Kims68Firebird

Re: Tire Rubbing Issue 68 Firebird - 02/20/19 04:48 AM

Front only
Posted By: Bob S.

Re: Tire Rubbing Issue 68 Firebird - 02/20/19 11:07 AM

I had a rubbing problem with 215-65-15’s on 15x7 r2’s on my 67. My friend ran the same setup on his 67 bird with no rubbing but his front end sits higher. I went with 215-70-14’s on 14x6 r2’s and no rubbing. 67’s and 68’s don’t have a lot of room for front tires. I think mine were rubbing on the outer wheelwells. Unfortunately whenever you deviate from stock on anything with FGF’s you can run into problems.
Posted By: FirebirdMike

Re: Tire Rubbing Issue 68 Firebird - 02/20/19 03:58 PM

I think for a 7" rim, ideally you want a 4.25" backspace with disk brakes (which push out the wheel .25" compared to drums). The one you linked, shows 3.76", so I'm guessing your rubbing is on the outside of the tire? One good thing working on your side is the narrow tread. You didn't mention the sidewall ratio, but hopefully it's a 65 series (60 would look kind of funny as it'd be pretty short, and 70 would be way to tall for a Firebird front and could allow rubbing).

So what can we improve without changing the wheels...

I'm guessing to, you are running the stock geometry, in which case you don't have the ideal camber gain, so the tire isn't leaning in under bump. Also, are the static camber setting somewhere within stock specifications, or do you have a performance alignment?

First couple things you can try is sell the husband, and use the money to replace the upper and lower ball joints with taller ones. Here's an example of the upper ones for reference: https://www.rickscamaros.com/camaro...KQ8MEAQYAiABEgKoj_D_BwE&gclsrc=aw.ds This will allow the tire to turn inward under compression, which not only will reduce potential to rub, but improve handling immensely.

Secondly, get a more modern alignment for radial tires: http://www.pozziracing.com/first_gen_suspension.htm#Alignment%20specs Follow the Guldstand "touring" specifications. This should also ensure more clearance fender to tire since it statically will lean slightly inward.

Third, you need to figure out how to get a front sway bar on there. Not only is that not safe for handling, but it's not helping control the tire movement.

If all this still doesn't solve it, then you need to replace the front wheels with something with more backspace. Unfortunately they don't sell that width with a deeper offset. And going wider still doesn't have the ideal offset, plus the 215 isn't recommended with anything wider than 7.5" rims. But usually you can get away with a 4.5" backspace on a 8" rim if you stay with 225/60.

Keep us updated.
Posted By: Kims68Firebird

Re: Tire Rubbing Issue 68 Firebird - 02/21/19 03:29 AM

Hey guys thanks for the quick responses! Lots to answer back to so I will try to make sure I answer it all.

Bob- Unfortunately, I can't run a 14" wheel, I vaguely remember something about that being in the instructions for the conversion kit. Thanks for the tip though!

Car is in storage right now and i'm too cold to go check but I want to say they are 215-60's. Not positive though. Could be 65 but I know not 70.

Yes it is rubbing on the top outer edge of the tire/ somewhat side.

Alignment is whatever the shop did. Silly I know, but I didn't know there were different alignment setups. Just thought it was simple- align the car so it stays in the lane. :P

Husband joke is pretty funny! Luckily he's a good one or I would have tried that already! wink

Ball joints and all the rest of the suspension was just changed when the conversion kit went in so I would like to try to avoid going that route if I can for now. Sounds like a good option for the near future though.

Modern alignment- sounds good. Will do.

Sway bar- working on it. I think I have it figured out, just have to bite the bullet and order one.

Unfortunately, no there are no deeper offset which is why I was suggested to buy those.

I think my next move is going to be to check if the spindles are in fact drop spindles and if so, get rid of them. I can adjust ride height later, it would just be nice to be able to have passengers again! smile

Thanks again for the help!
Posted By: Dennis in Indiana

Re: Tire Rubbing Issue 68 Firebird - 02/21/19 04:32 AM

Another point of reference for you. On my '68 I'm running BF Goodrich g-Force Super Sport All Season Radial; 225/45R17 mounted on American Racing Wheel Torq Thrust M Anthracite W/Machined Lip. 17" x 7" x 4" Back Space
Tire Part # 245WR7GFASXL-26483; Wheel Part #AR105M7761AML. Tire is 25" tall.
Front suspension is basically rebuilt stock, lowered by cutting the spring. I'm using an Addco 1 1/8” diameter front sway bar Part No. ACO-599 with KYB Gas Shocks Part No. KG4515. I'm running Wilwood disc brakes which move the hub out 3/8". Everything fits well.
It sounds like you need a little more back space in your wheels or shorter tires. According to BF Goodrich, 215 60R are 25.2" tall, 215 65R 26" tall and 215 70R 26.9" tall.

Hope this helps you sort it out.

Attached picture Firebird 2017-10-01 014.JPG
Posted By: Gus68

Re: Tire Rubbing Issue 68 Firebird - 02/21/19 11:26 AM

x3 You definitely need anti-sway bar. 14" rims would be better but I see that's not possible. Get stiff shocks. I don't think you want coil overs as you loose travel. 60's aren't helping as well. I think your main issue is the tires themselves. When you get to a certain width the tire wants to rub on the inner wheel well almost at the fender edge. If you had a skinny tire you would have lots of space for the tire to miss the inner fender.
You must be getting tire rub when you steer as well correct?

I would try going to a tire guy and have him swap out tires of various size onto your rims and check for rubbing. Take the best fitting tire given your configuration.

Good luck!
Posted By: Hank350

Re: Tire Rubbing Issue 68 Firebird - 02/21/19 03:12 PM

I'm not sure if the clearance is the same on a '69 or not.
Anyway, I have 215-65-15s on Ralley IIs and they rub in front but only when turning left into my driveway. It doesn't always happen and I can live with it. When I had similar diameter 14s on R IIs there was no rubbing at all.
Posted By: Kims68Firebird

Re: Tire Rubbing Issue 68 Firebird - 02/22/19 02:59 AM

Thanks Dennis. smile
I am pretty sure they are 215-60's so if I were to go to say a 225-45-15 that might work? I hesitate to get TOO small of a tire for the front because I don't want the stance to be too much lower in the front but I may end up having to. I am pretty set I think on ditching the drop spindles. I think they are causing a lot if not all of the problem but it's hard to say for sure. Unfortunately, there is no deeper backspace available on the Torq Thrust II's.
Posted By: Kims68Firebird

Re: Tire Rubbing Issue 68 Firebird - 02/22/19 03:05 AM

Gus-
Swaybar- yes! I have never worried about it because honestly the car steered like a dream and never had an issue cornering or turning with the other wheels. But now I see it is a must. Shocks are a possibility since they are fairly old and the car sat for a while before the current restoration. Probably won't do coilovers since I just put brand new springs on less than a month ago. What size tire would you suggest? I don't love the look of real small tires in front but I may have to deal. smile I don't usually get rubbing unless I am turning into a tight turn or there is a bump near the turn. Mainly when the body flexes or hits a dip. But of course that is probably due to no sway bar and maybe a combo of many things.
I like the idea of going to a tire guy, unfortunately, most are afraid of even touching CHROME "custom" wheels. Eyeroll!
Thanks for the suggestions!
Posted By: Kims68Firebird

Re: Tire Rubbing Issue 68 Firebird - 02/22/19 03:08 AM

Hank- I am guessing the drop spindles are the majority of the problem since you aren't having issues besides when you hit the driveway and neither are MOST FB owners that I have talked to. It is a mystery and probably a combo of problems but I hope to get them sorted out because I really love the look of these wheels and don't want to part with them. wink Thanks for letting me know!
Posted By: Dennis in Indiana

Re: Tire Rubbing Issue 68 Firebird - 02/22/19 03:40 AM

My front tires (17" rim diameter) are 25" tall which are pretty short but are only a 45 aspect ratio. (Sidewall height is 45% of 225mm tire width) Generally as rim diameter increases, height of the tire sidewall decreases. (aspect ratio) The idea was to keep relatively the same tire diameter as wheel diameters grew over time.

I'm no tire expert but don't think you'll find a 45 aspect ratio tire in a 15" rim. (would be a rubber band...) A 60 aspect ratio would be more common but still be a pretty short tire. That's probably going to be about the shortest tire you can get on a 15" rim. BF Goodrich has some handy info on their site. https://www.bfgoodrichtires.com/tire/bf-goodrich/radial-t-a

I think you are on to something with the drop spindles. Would be interesting to see how low your fender opening is to the tire - especially once tire diameter is confirmed.

x4 on the anti-sway bar. The Addco bar was the cheapest one I found. I think it makes a huge difference in the way the car drives. My car is not an autocross or track car but does see spirited driving on the street. It was kind of a PITA to install however.

As for the KYB shocks. Decent considering how inexpensive they are but they're kind of harsh.
Posted By: Kims68Firebird

Re: Tire Rubbing Issue 68 Firebird - 02/22/19 05:17 AM

Hopefully I did this right. Here is a picture of the car. https://ibb.co/Z6fwkvj

Not the best for looking at the gap between fender and tire but it's the best I have for now and it has actually increased a little since I changed the springs.

I know nothing of tire sizes so I was just taking a guess after googling the size. They do exist but you are probably right that it would be short.

Sway bar- why was it such a hassle?

KYB- Harsh how?
Thanks again Dennis!
Posted By: Bronze Bird

Re: Tire Rubbing Issue 68 Firebird - 02/22/19 05:22 PM

Don't change anything until you install the sway bar and re-evaluate the problem.
Posted By: FirebirdMike

Re: Tire Rubbing Issue 68 Firebird - 02/22/19 06:18 PM

225/45R15s would be stupid short. Any tire 25" or shorter in diameter will look out of place, especially in the rear. The reason I recommended a 225/60 was compatibility with the width of the 8" TTIIs that have more offset to bring the tire in more overall.

One more thing you could look at (since you mentioned body flex) are the front subframe mounts. If those are worn (and they often are because people forget about them), then you're going to get a lot more movement than just the suspension. Mine were still the original when I bought my car, and they practically fell apart they were so worn. I replaced them with interlocking aluminum and wow, what an improvement! Really took out the body lean without hurting the ride.

Which leads to my next point, there are more durable materials available now besides rubber. Some people use polyurethane as an upgrade because they're concerned about too much stiffness. My experience is, rubber and poly don't do anything to dampen motion that's going to be noticeable in terms of ride comfort. Heck if your bushings are more than 10 years old, it's probably making the ride worse. I recommend delrin material (currently only used by BMR), or aluminum (available through many manufacturers). If using subframe connectors, only use delrin or aluminum.
Posted By: Kims68Firebird

Re: Tire Rubbing Issue 68 Firebird - 02/23/19 02:36 AM

Thanks Bronze Bird and Mike.
I am going to try sway bar first for sure.

Tires- Rear tires/ wheels aren't rubbing, only the front. But no I would never put that small in the back. They are larger than the fronts now.

Already changed to aluminum so it's probably not that. Thanks for the suggestions though.
Posted By: salmon38

Re: Tire Rubbing Issue 68 Firebird - 02/23/19 07:38 AM

Originally Posted by Dennis in Indiana
Another point of reference for you. On my '68 I'm running BF Goodrich g-Force Super Sport All Season Radial; 225/45R17 mounted on American Racing Wheel Torq Thrust M Anthracite W/Machined Lip. 17" x 7" x 4" Back Space
Tire Part # 245WR7GFASXL-26483; Wheel Part #AR105M7761AML. Tire is 25" tall.
Front suspension is basically rebuilt stock, lowered by cutting the spring. I'm using an Addco 1 1/8” diameter front sway bar Part No. ACO-599 with KYB Gas Shocks Part No. KG4515. I'm running Wilwood disc brakes which move the hub out 3/8". Everything fits well.
It sounds like you need a little more back space in your wheels or shorter tires. According to BF Goodrich, 215 60R are 25.2" tall, 215 65R 26" tall and 215 70R 26.9" tall.

Hope this helps you sort it out.



Nice wheel choice for a FGF, by the way.
Posted By: Dennis in Indiana

Re: Tire Rubbing Issue 68 Firebird - 02/23/19 02:40 PM

Sway bar was difficult to “thread” into the frame. It was one of the updates I did prior to ripping the car apart and totally redoing.
KYB shocks at stiff. They transmit a lot of little road bumps from the awful Midwest roads.
Posted By: Dennis in Indiana

Re: Tire Rubbing Issue 68 Firebird - 02/23/19 02:45 PM

Thanks Salmon38. Love/hate relationship. I don’t necessarily like the short sidewall, big rim look on old cars. And sometimes I think the tires look too small. Then I’ll see it in a different light and really like it. I’m a traditionalist in a modern world. Lol
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