Tire selection for 74 big block

[basilio]

OK its time to select new tires. Presently the '74 convertible has Michelin X 215/75/15 (from previous owner on original rims) which are very old and are making noises.

225/70/15 seems to be a logical choice to replace the original GR70/15. In "performance" tires in 225/70/15 Goodyear has Eagle 2, GT+4 if you can find it, and the RSA. BF Goodrich has Radial T/A. Firestone has the Firehawk Indy. Dunlop has its equivalent. Unfortunately, for all of these tires except one at this size acccording to the respective manufacturer's web sites state that they are for 7.5 inch maximum rim width!!!!! The only tire at this size that I have found that is stated to take the 8 inch rim is the RSA. Does anyone have any experience with this tire? It does not look like a tire that belongs on a C3.

An alternate size is 235/65/15. Goodyear has Eagle GA but it is a "touring" tire made for comfort not real performance.

I do not want to go to any wider tires such as the 255/60/R15 for possible cleareance issues.

Has anyone had problems with 225/70/15 Eagle 2 or Radial T/A or Firehawk Indy with the stock 8 inch rims?

Any advice would be appreciated.

 

[Koop]

I've never had Firestones that I liked, the Eagle GA is for women, the Eagle 2 is a very good tire, but I recently switched (from 245 60 15 Eagle 2) to Michellin Pilots, 235 60 15. Big improvement over the Goodyear, they don't have raised white letters but they handle much better and the C3 needs all the extra grip it can get (especially with that 454).

 

[gmb074]

I have 235/60/15 w/raised letters on my '74 roadster made by goodrich. I do not have any clearance problems but again mine is not a big block. They seem to stick well and corner well.Hope this helps.

 

[lnirenberg]

OK its time to select new tires. Presently the '74 convertible has Michelin X 215/75/15 (from previous owner on original rims) which are very old and are making noises.

225/70/15 seems to be a logical choice to replace the original GR70/15. In "performance" tires in 225/70/15 Goodyear has Eagle 2, GT+4 if you can find it, and the RSA. BF Goodrich has Radial T/A. Firestone has the Firehawk Indy. Dunlop has its equivalent. Unfortunately, for all of these tires except one at this size acccording to the respective manufacturer's web sites state that they are for 7.5 inch maximum rim width!!!!! The only tire at this size that I have found that is stated to take the 8 inch rim is the RSA. Does anyone have any experience with this tire? It does not look like a tire that belongs on a C3.

An alternate size is 235/65/15. Goodyear has Eagle GA but it is a "touring" tire made for comfort not real performance.

I do not want to go to any wider tires such as the 255/60/R15 for possible cleareance issues.

Has anyone had problems with 225/70/15 Eagle 2 or Radial T/A or Firehawk Indy with the stock 8 inch rims?

Any advice would be appreciated.

I had RSAs on an Audi OEM and they were absolute POS--short tread life, low grip terrible combination. My $.02, especially with a big block, you want lower profile tires as the 70 or 75s have way too much side wall flex. Also, I would avoid anything with an S or T speed rating as the compounds are too hard for good all around performance. Tire rack shows some decent speed rated tires @ 235/60-15 but not in any other 15s applicable size. 235/60-15s are about 1 1/2 inches shorter than the tires you have on now which will screw up your speedo by overstating speed by 4 mph +/- and leave you with more wheel well space. You are truly caught between a rock and a hard place as it is really difficult, in my humble opinion, to find good performing tires w/15X8 rims. I solved this by going to 16X8 but it gets pricey.

The good news, however, is I finally rescued my baby from its winter hibernation spot and wouldn't you know its raining.

 

[basilio]

big block tires for '74

Thanks for the help but unfortunately 235/60/15 and 245/60/15 are up to 5% smaller in diameter and this will throw the speedometer off not to mention other issues such a safety--see tires1010. With regards to the RSA, I will stay away from it.

I may have to settle for BFG Radial T/A or the Goodyear Eagle 2 or GT+4 although it may officially fall outside the specs. A specialist at Goodyear said it shouldn't matter anyways. BFG was non commital saying the car calls for 225/70/15. Which is a better tire the T/A or the Eagle 2?

Unfortunately the Eagle GT+4 in that size is no longer made. Is this a better tire than the former two for this car and would anyone buy them if they could be located? Thanks.

 

[Eric]

Go to the top of this page and click on the "Home" link. Then scroll down and hit the Tire Rack link on the left side. Shop by size for the 225/70/15 and then compare the feedback and other ratings. The Firehawks kick everything else in nearly every category. I had them on my old 71 and they gripped way better than the Dunlop GT Quals that were on it when I got it. And even though you may never drive it in the rain, they have great wet traction (had them on my old daily Z24 too).

You will find that the 225 size really fills the wheel wells nicely and give the car a nice stance from the front and rear since they are a little wider than stock but not so much that there is a rubbing issue.

BTW, I had them on the stock 8 inch rims and they were fine. I think 225/70/15 became the stock size later in the 70's anyhow and the rims were still 8".

Good luck in your search!

 

[pgtr]

OK its time to select new tires. Presently the '74 convertible has Michelin X 215/75/15 (from previous owner on original rims) which are very old and are making noises.

Indeed.

225/70/15 seems to be a logical choice to replace the original GR70/15. In "performance" tires in 225/70/15 Goodyear has Eagle 2, GT+4 if you can find it, and the RSA.

Your instincts are dead on regarding 225/70R15 as the logical choice. Only the RSA choice you listed is a performance tire. The others are entry level minimal standard radials which are definately not performance tires by any stretch.

BF Goodrich has Radial T/A. Firestone has the Firehawk Indy. Dunlop has its equivalent.

None of these are performance tires either. FStone does offer an excellent tire in your size - the PV41.

Unfortunately, for all of these tires except one at this size acccording to the respective manufacturer's web sites state that they are for 7.5 inch maximum rim width!!!!! The only tire at this size that I have found that is stated to take the 8 inch rim is the RSA. Does anyone have any experience with this tire? It does not look like a tire that belongs on a C3.

It is an excellent tire. Your C3 originally shipped w/ G70 sized tires. The G70 size of the 1970s IS the exact same size as the current modern 225/70R15 radial. Standards have changed since the 1970s as to how the calculate maximum rim width even though the same tire dimensionally is available. The best you can do is stick w/ the 225/70R15. Most are rated at up to 7" or 7.5" and of course the one GY is still rated at 8".

An alternate size is 235/65/15. Goodyear has Eagle GA but it is a "touring" tire made for comfort not real performance.

Dimensionaly it's got fewer RPMs than the correct size for your car and a larger OD - may fit but is taller - not aware of any good tire options in this size but I haven't looked closely at it.

I do not want to go to any wider tires such as the 255/60/R15 for possible cleareance issues.

Has anyone had problems with 225/70/15 Eagle 2 or Radial T/A or Firehawk Indy with the stock 8 inch rims?

Any advice would be appreciated.

255/60 will potentially have clearance issues (or not) and there are no performance tires avail in this size save one Pirelli. in 225/70R15 there are at least 5 decent tires still available including the GSA, PV41, General XP2K, Cooper Cobras, Sumitomo HTR 200, Michelin Pilot XGT H4s. Beyond those, the overwhelming majority of the tires in these sizes offer little more than performance looking sidewall treatments, hard rubber compounds, poor dry adhesion and lateral handling characteristics.

Look for a 225/70R15 with a MINIMUM of an A-temperature rating, H-speed rating (or V better yet), and treadwear somewhere in the 300s give or take as a decent starting point. It will be a stronger tire, have better carcass integrity, better lateral adhesion, better handling characteristics and feedback as well as better dry adhesion.

 

[Bill75]

Same Tire Question

I was just about to post a question about tires and ran across this thread. I'm looking to upgrade mine also, not especially because of HP but for comfort. I have Firehawk P225/70R15's now and they ride like they're made of cast iron. I can feel it when I hit an acorn! The tire rating is marked 100S and the car handles poor, bump steer is really bad. So I was hoping for a suggestion also, I looked at Tirerack's page and didn't see anything that impressed me too much. Am I stuck with this kind of ride because of the 15 in wheel and the available tires for it?

pgtr, what did you finally end up with?

Hope I'm not stealing your thread but it looked like a good discussion.

Bill

 

[pgtr]

As you've noticed those are S-speed rated (B-temp), not a performance tire by any stretch.

I always suggest considering ANY H or V speed rated all-season performance tire however in our size of 225/70R15 this limits us to:
Goodyear Eagle RS-A
Goodyear Eagle RS-A 'Plus'
Firestone PV41
General XP-2000 V4
Sumitomo HTR 200
Michelin Pilot XGT H4

Tirerack can be OK for research and filters based on speed ratings but they don't carry all tires and they do quite often make mistakes in their data.

However a couple of caveats in your case... are your shocks OK? Also a performance tire can deliver a firmer ride while a non-performance basic hwy radial (like the Firehawks) can give a softer ride (if somewhat 'mushier' or imprecise in responsiveness).

If you are comfortable w/ the current brand you have you can step up to the PV41's from Firestone - it's a very good V rated performance tire. The General XP2K is another V rated one. The H rated Michelin Pilot should be comparable - in your case that might be a good compromise...

 

[Bill75]

I'll do some research on your suggestions, thank you!

I've rebuilt the entire suspension on this car; new front springs, shocks all the way around, power steering, tie rod ends, ball joints, all new bushings, etc. Swing arms in the rear, U-joints on half shafts, rear end rebuilt etc. So things should be pretty much up to par. I wasen't too encouraged when you stated the performance tires would offer a somewhat stiffer ride as compared to the Firehawks S speed rated ones I have, so maybe I'm looking for something that isn't achievable in a C3. But I'll look into it some more........I appreciate your response.
Best regards

Bill

 

[JJS]

I had (still have 'em) Goodyear GT +4's in "like new" condition when I got my car, and didn't like them a bit. They were VERY loud, and loose....no traction. They were also really wide, and the front tires would hit the wheel wells on short radius turns. That wide look did look nice, but, they just didn't cut it on the performance/handling end.

I went with a more stock tire last year, and chose the Firestone Firehawk Indy 500's.
I was a bit hesitant to go with Firestone after what happened with the SUV tires a few years back, and also because there was a LOT of white (raised white lettering)....I was thinking maybe too much.

But these tires have been great! They hold the road, they're not noisey like the Goodyear's, and I've had more compliments about them than I did with the previous set. They really look nice on the car, and if I had to do it over again, I'd go with the Firestones in a heartbeat.

 

[74bigblock]

I'm running the 255/60-15's Indy. No clearance issues. Ride great, and the width gives you a little extra grip. I would recommend this size. Let the tire store worry about your clearance issues.... have them mount and check. You should be fine though, and it will remedy the height issue you are concerned about.

 

[pgtr]

I'll do some research on your suggestions, thank you!

I've rebuilt the entire suspension on this car; new front springs, shocks all the way around, <SNIP> all new bushings, etc.

Bill, did you use OE or OE-like components in the above or aftermarket/upgrade/performance fare such as HD springs, poly bushings, HD or performance shocks etc...?

I wasen't too encouraged when you stated the performance tires would offer a somewhat stiffer ride as compared to the Firehawks S speed rated ones I have, so maybe I'm looking for something that isn't achievable in a C3. But I'll look into it some more........I appreciate your response.

The improvement in handling and precision w/ a quality tire is an order of magnitude over the non-performance fare but the difference in ride quality all other things being equal won't be 'that' much. Actually I'm curious about the other components as possible causes...?

I'm very pleased w/ base stock OE componentry and modern performance rubber on a street driven C3.

 

[pgtr]

Couple things to clarify here...

I'm running the 255/60-15's Indy. No clearance issues.

On a pre '78 C3, 255/60R15s are a crap shot as to fit and clearance. The factory in 1978+ trimmed the fiberglass back to allow the 255s to fit. Some people (myself included) have fit 255s w/o a problem - albeit w/ no margin whatsoever and others have immediately hit (no pun intended) up against clearance issues. Almost any pre 78 will have some rubbing somewhere especially at lock over a harsh bump - that's all but guaranteed even if the fenders seem to clear initially.

Ride great, and the width gives you a little extra grip. I would recommend this size.

I mostly disagree w/ this. The ONLY 255/60R15 that could compare w/ a good 225/70R15 such as the PV41 or XP2Ks or Pilots as to 'grip' is the Pirelli Zero SUV tires. ANY 'other' 255/70R15 is purely non-performance highway radial w/ weak sidewall construction and hard rubber compound and low speed rating. In any sort of objective comparison as to lateral adhesion, these 255s will simply NOT be comparable to the specific 225s I've listed above. In short there is a comparative reduction in lateral grip when compared to a true performance 225/70. [note that the one expection to this would be the Pirellis]

Actually I just remembered - I 'think' Kumho makes some decent 255/60s. But unfortunatley other than those 2 possible tires - this is a dead-end size offering no real performance potential.

Let the tire store worry about your clearance issues.... have them mount and check. You should be fine though, and it will remedy the height issue you are concerned about.

Simply dropping the front end on the ground and checking the fenders may not be sufficient. The tires can crash while in a tight turn especially over a bump and that may potentially damage the fiberglass...? On the other hand a little rub or 'polish' on some carriage bolts on the frame might be tolerable. In short be careful and don't assume this size will fit on any pre '78 too casually.

 

[Bill75]

Bill, did you use OE or OE-like components in the above or aftermarket/upgrade/performance fare such as HD springs, poly bushings, HD or performance shocks etc...?

pgtr,

All the parts used were OE, no aftermarket stuff except for two things: the shocks are KYB gas shocks and we used poly bushings on the strut rods only, everything else was OE rubber. I must say I haven't had a 4 wheel alignment yet, the car tracks straight going down the road, maybe some of the bump steer will be corrected when I get it aligned properly.
Bill

 

[pgtr]

That sounds like a pretty ideal set up in my opinion. I doubt a 4 wheel alignment will affect ride - at least not that much. Some people concentrate on radical suspension mods that yields a bone jarringly harsh ride and then use very cheap non performance tires. To the contrary an essentially stock suspension (like yours) and awesome tires yields superior handlings w/o the drawbacks. I doubt a set of performance tires will make that much of a noticeable difference in ride quality. Gas charged KYBs might yield a 'firmer' ride compared to say an entry level mass market brand shock. Can't comment on the poly's on the strut rods. Bottom line is I would not expect upgrading to perf tires to make the 'ride' noticeably worse - or better (though a very big difference in handling and safety will be realized). Don't know what tire pressures you're running but I usually run about 32 or so. A little less will soften up the ride a bit.

 

[74bigblock]

Sometimes... I wanna