TIRE experts - I need help!

[glazounov]

Hi everyone!

I have a totally STOCK 1994 LT1 convertible - stock “sawblade” wheels, etc. I would like to go with new tires that are just a tad wider than the stock front-225/45ZR17 rear-285/40ZR17. Are there any adverse or negative effects to going to a tire that would be just about an inch wider all around? Will I have wheel–well clearance problems? Suspension problems? Handling problems? More importantly, can these stock wheels HOLD anything larger ... or will I need to buy wider wheels also? What is your experience? Any recommendations?

I’m thinking 315/35XR17 on the back (lower aspect ratio so I don’t screw up my speedometer - right?), but do I need an 11 inch rim for this? Would 255/40 ZR17 be a good complement to this on the front?

Also ... what problems might be caused by leaving the front tires stock and going wider on the rear?

No racing for me, just street and highway driving. I’m looking to enhance cornering and “appearance” WITHOUT enhancing the dreaded “road noise” ... is that possible? I’m kinda new to this, so I appreciate the input of all you “experts” out there.

Thanks! Denny

 

[Moonunit 451]

I think 315's are probably to wide for your rears if you want decent wear on 9.5 rims. 285's would be OK on the front and rear.

 

[garycr14]

Tires

Hi,
I have 315's on the rear of mine, too late to check the exact size, don't remember off the top of my head, actually they are all 4 the same currently with no adverse effects. I had 270/40 17's all around before and looked and drove fine, no clearance problems. I am going to go back to the 270's in the front, I think it will look better, I'll find out about the handling after I put them on. I got a great deal on the 315's is why I put them all around, had to buy the set, but I don't like the look of them up front. They are too tall for the front appearance wise.

 

[SPANISHVETTS]

I just put Firestone ZS50 285/40/17´s on the back of the 90. Tire Rack told me that 285s were the largest I could put on the 9.5¨ rims. They are 10 times stickier than the Dunlop 9000´s that I was running. This was a tough move since Mr.D is so generous with handouts to the Team. I still have the 275/40/17 Dunlops on the front. I do not notice any difference in handling between the two and the drone from the 383 + the 400 watt MP3 player makes road noise a non-issue:L

 

[c4cruiser]

3215/35 tires will really need an 11-inch rim for them to look right and not have any excessive bulging of the sidewall. Your rear wheels can be moved to the front to mount the 285 tires but check carefully for clearance in the fenderwells. Also, all tires do not necessarily have the same tread width for a given size. Use the Tire Rack's specification pages to see the physical dimensions of the tires by size. The speedometer will not be affected by this as readings depend on the tire diameter, but the width does look different is some cases. For example, the Firestone SZ50 tire is nearly a full inch narrower in a 275/40-17 size compared to a Kuhmo Estca MX in the same size.

AFS Wheels ( www.afswheels.com ) makes a ZR-1 style wheel with the same offset used on the 96 Grand Sport coupe (GS verts did not use the 11" wheel) that will fit in the rear wheelwells. However this wheel will cause a small amount of tread to stick out past the wheel well. You could add the GS rear flares to cover it.

Road noise is more of a function of the tread design than size. Some tires are quite noisy, others are super-quiet. The factory went to a narrower front tire/wheel to help reduce the "darting" or tracking you see when the tires get caught in the troughs in the road surface. A 275 tire in the front will cause more of this but it can also be reduced by adding and extra 1/16" toe-in in the front.

 

[Tuna]

In 94, the Z07 optioned cars came with 9.5 wheels all around and 275/40 tires. You can install the 9.5 wheels and either 275 or 285/40 tires up front without any problems. Most tire companies advise against mounting the 275 or 285 or the 8.5 wheel - I've seen it done but it just doesn't look right to me.

As for the rear, the 315/35/17 will work on the rear with the 11" wheel. You'll need a wheel with a 50mm offset like the Grand Sport wheel if you don't want them sticking out. If you use a wheel with less offset like the 36mm from the ZR1 wheel, they will stick out a bit. I have this combo on my car and I installed the GS flares to provide a little extra coverage to the tire.

Unless you want to track down 91-93 ZR1 rears which match your existing sawblades, you'll be looking at buying 4 new wheels. You might want to find 2 9.5 sawblades and mount the same size tire (275/285) on all four.

For balance, if you go with the 11" rears, please move your existing 9.5 rears to the front with the 285 tires.

 

[garycr14]

315's

Hi,

I have 315/35ZR-17's on my "94" with the stock wheels. They do not fit or look right on the front, so I will be replacing with 270/40's which I had on before. The 315's look good on the rear with the stock wheels. I get complements on them all the time.

 

[Tuna]

Hi,

I have 315/35ZR-17's on my "94" with the stock wheels. They do not fit or look right on the front, so I will be replacing with 270/40's which I had on before. The 315's look good on the rear with the stock wheels. I get complements on them all the time.

I just checked some of the tire specs on the TireRack.com website for different tires for recommended rim width and noted that 10.5" seems to be the minimum recommended width for the 315/35/17 tire.

Even the 275/40/17 has a minimum recommended rim width of 9".

Mounting 315's on 9.5 or even 8.5 may work but is it really safe. It's your car and your life. If something goes wrong with your tire/wheel combination, don't blame the tire company if you have them mounted on wheels that are less than recommended width.

 

[JRMaroon]

Denny,


You stated in your original post that your fronts were 225's. The stock fronts on my '94 are 255/45/17 so you can go at least this wide on your rims.(Assuming they are stock)

Jeff

 

[glazounov]

I think 315's are probably to wide for your rears if you want decent wear on 9.5 rims. 285's would be OK on the front and rear.

Thanks, Moonunit 451 - I think you might be right.

Denny

 

[glazounov]

Hi,
I have 315's on the rear of mine, too late to check the exact size, don't remember off the top of my head, actually they are all 4 the same currently with no adverse effects. I had 270/40 17's all around before and looked and drove fine, no clearance problems. I am going to go back to the 270's in the front, I think it will look better, I'll find out about the handling after I put them on. I got a great deal on the 315's is why I put them all around, had to buy the set, but I don't like the look of them up front. They are too tall for the front appearance wise.

Hi - Are you using the stock rims?

Denny

 

[glazounov]

3215/35 tires will really need an 11-inch rim for them to look right and not have any excessive bulging of the sidewall. Your rear wheels can be moved to the front to mount the 285 tires but check carefully for clearance in the fenderwells. Also, all tires do not necessarily have the same tread width for a given size. Use the Tire Rack's specification pages to see the physical dimensions of the tires by size. The speedometer will not be affected by this as readings depend on the tire diameter, but the width does look different is some cases. For example, the Firestone SZ50 tire is nearly a full inch narrower in a 275/40-17 size compared to a Kuhmo Estca MX in the same size.

AFS Wheels ( www.afswheels.com ) makes a ZR-1 style wheel with the same offset used on the 96 Grand Sport coupe (GS verts did not use the 11" wheel) that will fit in the rear wheelwells. However this wheel will cause a small amount of tread to stick out past the wheel well. You could add the GS rear flares to cover it.

Road noise is more of a function of the tread design than size. Some tires are quite noisy, others are super-quiet. The factory went to a narrower front tire/wheel to help reduce the "darting" or tracking you see when the tires get caught in the troughs in the road surface. A 275 tire in the front will cause more of this but it can also be reduced by adding and extra 1/16" toe-in in the front.

Thanks c4cruiser ... good info! I'll check out AFS right away. Do they make the stock wheel in an 11" size?

 

[glazounov]

Unless you want to track down 91-93 ZR1 rears which match your existing sawblades, you'll be looking at buying 4 new wheels. You might want to find 2 9.5 sawblades and mount the same size tire (275/285) on all four.

For balance, if you go with the 11" rears, please move your existing 9.5 rears to the front with the 285 tires.

Thanks Tuna,

Maybe I'll look for the ZR1 rears and do exactly what you said. THANKS!

 

[glazounov]

I have 315/35ZR-17's on my "94" with the stock wheels. They do not fit or look right on the front, so I will be replacing with 270/40's which I had on before. The 315's look good on the rear with the stock wheels. I get complements on them all the time.

Really? I've seen opinions here that 315's are too wide for the stock 9.5 wheels. Are you running 9.5 stock wheels on the rear?

Denny

 

[glazounov]

I just put Firestone ZS50 285/40/17´s on the back of the 90. Tire Rack told me that 285s were the largest I could put on the 9.5¨ rims. They are 10 times stickier than the Dunlop 9000´s that I was running.

Thanks! I have Firestones on right now, but have heard really good reviews of the Goodyear Eagle F1 GS-D3. Anyone else want to weigh in with an opinion?

 

[glazounov]

Mounting 315's on 9.5 or even 8.5 may work but is it really safe. It's your car and your life. If something goes wrong with your tire/wheel combination, don't blame the tire company if you have them mounted on wheels that are less than recommended width.

Yeah - I agree. Safety is a big concern of mine.

Thanks for your time! Denny

 

[glazounov]

You stated in your original post that your fronts were 225's. The stock fronts on my '94 are 255/45/17 so you can go at least this wide on your rims.(Assuming they are stock)

Jeff

Jeff ... OOOOPS! You are correct! That was a TYPO on my part! I really did mean 255 ... NOT 225.

Thanks for pointing that out!

Denny

 

[garycr14]

Rims

Hi - Are you using the stock rims?

Denny

I do not know what the size of my rear rims, I will measure when I have a chance. They seem to fit fine, but the fronts are too big, obvious crowning, which is why they will be comming off this week.