Wheel and tire conundrum
06-19-2013, 10:07 PM
#1
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Wheel and tire conundrum
Alright, so I bought this "project" car and it's in need of new front tires. Here's the delema: I have an 8.8 with 5 lugs on the rear on Mustang 16" wheels. On the front, there are 17" cheap wheels.
Option 1) just buy new 17" wheels, of which there are few options.
Option 2) Buy new wheels and tires and hope they will still make them when I get around to doing the rear end
Option 3) buy a full set to be safe
I'm thinking option 2, but I don't know what tire to get. I'm pushing the limits of traction on the 255's on the rear (it sits high so I can get away with it). But now it's 16" or 15" wheels. I've read so much around the internet that I don't know what's right any more. Thankfully, There are experts in the matter.
I was thinking a 16"x7.5 (light wheel) with a 38mm offset and a 235/40R16. Is there anyone that makes that tire, did I get it right, how far off am I, etc? I did see the 15" wheel posts, but I also saw that 225 isn't enough width, hence the trying for a 16" with 235s.
Thanks!
Option 1) just buy new 17" wheels, of which there are few options.
Option 2) Buy new wheels and tires and hope they will still make them when I get around to doing the rear end
Option 3) buy a full set to be safe
I'm thinking option 2, but I don't know what tire to get. I'm pushing the limits of traction on the 255's on the rear (it sits high so I can get away with it). But now it's 16" or 15" wheels. I've read so much around the internet that I don't know what's right any more. Thankfully, There are experts in the matter.
I was thinking a 16"x7.5 (light wheel) with a 38mm offset and a 235/40R16. Is there anyone that makes that tire, did I get it right, how far off am I, etc? I did see the 15" wheel posts, but I also saw that 225 isn't enough width, hence the trying for a 16" with 235s.
Thanks!
06-20-2013, 08:20 AM
#2
Jim Stainer
It is most unfortunate that no one makes anything wider than 225/45-15s for these cars. The problem is there are no factory production cars that use them to support a wider size. For example because the Corvette has used wide low profile tires for that last couple decades the guys in Camaro and Mustang world have lots of great tires available to them. But our little Miatas have no such benefactor.
I too have been reading and searching for wheels and tires for months and IMO the best that is available falls far short of what would be ideal for my car. I also considered 15,16 and 17 wheels but the 16 and 17 inch tires available are so tall I felt they would not be a good choice for me. So I’m running 15x9 +36 wheels with 5mm spacers and 225/45-15 Rivals. If it existed I’d love to have 275/35s on 10" wheels but there is no such street tire.
IMO I would not let 10mm difference in tire width push me to new wheels and 7.5 wide wheels are too narrow for 235s. A good rule of thumb is the optimal rim is the same size as the tread width (not section width) rounded up to the nearest half inch. So the 225/45-15s I am running have a tread width of 8.5" and will fit fine on either an 8 or 9" wheel but will perform better on a 9. (As noted in Grassroots motor sports testing) I'm sure you know the size you are looking for 235/40-16 dosn't exist so you can't really shop for rims based on that size.
The bottom line is there are no decient wide low profile street tires for our cars. Let us know what you end up with and good luck!
I too have been reading and searching for wheels and tires for months and IMO the best that is available falls far short of what would be ideal for my car. I also considered 15,16 and 17 wheels but the 16 and 17 inch tires available are so tall I felt they would not be a good choice for me. So I’m running 15x9 +36 wheels with 5mm spacers and 225/45-15 Rivals. If it existed I’d love to have 275/35s on 10" wheels but there is no such street tire.
IMO I would not let 10mm difference in tire width push me to new wheels and 7.5 wide wheels are too narrow for 235s. A good rule of thumb is the optimal rim is the same size as the tread width (not section width) rounded up to the nearest half inch. So the 225/45-15s I am running have a tread width of 8.5" and will fit fine on either an 8 or 9" wheel but will perform better on a 9. (As noted in Grassroots motor sports testing) I'm sure you know the size you are looking for 235/40-16 dosn't exist so you can't really shop for rims based on that size.
The bottom line is there are no decient wide low profile street tires for our cars. Let us know what you end up with and good luck!
Last edited by charchri4; 06-20-2013 at 08:53 AM.
06-20-2013, 11:50 AM
#3
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Yeah, I found that out afterwords. I'm trying to find as wide of a wheel I can fit on the Miata. But right now the 17's on the front are not just goofy, but heavy. I've also read the Miata is very heavily effected by unsprung weight. I've found wheels in 16" that will fit, but I can find tires wide enough.
The short story of this is 16" wheels, if light enough, are very well suited for the Miata, but no tire exists for a wheel that is wide and short enough to fit that rim.
I've read you can get up to a 245 width, but that requries a 17" wheel, hence my thinking of a 235 on a 16". But 17" wheels are too heavy (an goofy looking).
A 245/50R16 DOES exist, but that might be too tall, especially if lowered. If not, then a very wide rim with a large offset would be required, assuming you can find a wheel at 18 pounds or less (the number I read to be the limit due to unsprung weight). On another note, my rears are 225/55R16's I was mistaken in the size on that. Those are rather large. So those would be even larger and won't fit up front. (Again, solid rear axle causes the rear to sit a little higher.)
There was some good 16" tire size but it seems to have gone away, something to do with "vintage" Porches. There are some racing tires I found that that are close, too, but those are spendy for a mostly commuter car.
Sorry for "typing out loud." I'm trying to find the best compramise. But I have a feeling that I will have to settle for the same wheels that everyone else has, 225/45R15. Can you confirm this? This makes me quite sad
The short story of this is 16" wheels, if light enough, are very well suited for the Miata, but no tire exists for a wheel that is wide and short enough to fit that rim.
I've read you can get up to a 245 width, but that requries a 17" wheel, hence my thinking of a 235 on a 16". But 17" wheels are too heavy (an goofy looking).
A 245/50R16 DOES exist, but that might be too tall, especially if lowered. If not, then a very wide rim with a large offset would be required, assuming you can find a wheel at 18 pounds or less (the number I read to be the limit due to unsprung weight). On another note, my rears are 225/55R16's I was mistaken in the size on that. Those are rather large. So those would be even larger and won't fit up front. (Again, solid rear axle causes the rear to sit a little higher.)
There was some good 16" tire size but it seems to have gone away, something to do with "vintage" Porches. There are some racing tires I found that that are close, too, but those are spendy for a mostly commuter car.
Sorry for "typing out loud." I'm trying to find the best compramise. But I have a feeling that I will have to settle for the same wheels that everyone else has, 225/45R15. Can you confirm this? This makes me quite sad
06-20-2013, 01:02 PM
#4
Jim Stainer
LOL yeah I feel your pain big time! I'm glad to be a sounding board for you. The problem we all face is the best compromise still stinks!!
I agree 245/50s would be too tall especially if you lower it some. I also agree that 15s and 16s look at home on NAs and NBs but some how 17s just look a bit out of place and fugley on them.
But let me bounce something else off you. Paraphrasing again from grassroots wheel weight can be important but it makes a much bigger difference in ride quality than it does in performance. As I recall grassroots had 8 lbs of wheel weights on each wheel before they noticed a difference and at that it was only a 10th of a second difference in a 70 second autocross. Most guys do more damage to their time than that by the apex of the first corner!
The way to consider wheel weight is in the total percentage of unsprung weight to sprung weight. Your brakes, control arms and spindles weigh far more than your wheels and few spend guys a bus load of money to lighten them.
So if you consider wheel weight as a percentage of sprung weight you might see a slight difference from a 10 lb wheel to a 20 lb wheel, probably in the feel of the steering wheel going over bumps, but a 14 to 15 pound wheel you never will notice the difference. With 400 ft pounds of torque from a V8 slinging them around I would bet you triple your current wheel weight and not tell the difference in performance.
I do have a little real world experience with this in my Camaro. I went from 16x8s with 245/50s to 17x9 with 275/40s to 18x10.5 with 295/30s over 2 seasons. Each move added several pounds per wheel in weight but also added significantly better performance and grip. There is no question at all that given the choice between wheel weight and width I'd go with width every time. But even so the compound of the tire makes far more difference. Race rubber on 17x9s would beat my decient performace street tires on the 18x10.5s Been there done that too...
Now if you have not read everything on the web yet about this check out this article on FB:
https://www.facebook.com/notes/holli...45008598916447
Skip down about half way to optimal wheel size and dig in. There is a lot of really good stuff on this page!
I agree 245/50s would be too tall especially if you lower it some. I also agree that 15s and 16s look at home on NAs and NBs but some how 17s just look a bit out of place and fugley on them.
But let me bounce something else off you. Paraphrasing again from grassroots wheel weight can be important but it makes a much bigger difference in ride quality than it does in performance. As I recall grassroots had 8 lbs of wheel weights on each wheel before they noticed a difference and at that it was only a 10th of a second difference in a 70 second autocross. Most guys do more damage to their time than that by the apex of the first corner!
The way to consider wheel weight is in the total percentage of unsprung weight to sprung weight. Your brakes, control arms and spindles weigh far more than your wheels and few spend guys a bus load of money to lighten them.
So if you consider wheel weight as a percentage of sprung weight you might see a slight difference from a 10 lb wheel to a 20 lb wheel, probably in the feel of the steering wheel going over bumps, but a 14 to 15 pound wheel you never will notice the difference. With 400 ft pounds of torque from a V8 slinging them around I would bet you triple your current wheel weight and not tell the difference in performance.
I do have a little real world experience with this in my Camaro. I went from 16x8s with 245/50s to 17x9 with 275/40s to 18x10.5 with 295/30s over 2 seasons. Each move added several pounds per wheel in weight but also added significantly better performance and grip. There is no question at all that given the choice between wheel weight and width I'd go with width every time. But even so the compound of the tire makes far more difference. Race rubber on 17x9s would beat my decient performace street tires on the 18x10.5s Been there done that too...
Now if you have not read everything on the web yet about this check out this article on FB:
https://www.facebook.com/notes/holli...45008598916447
Skip down about half way to optimal wheel size and dig in. There is a lot of really good stuff on this page!
Last edited by charchri4; 06-20-2013 at 01:11 PM.
06-20-2013, 02:19 PM
#5
V8 Miata Participant
I have an NA with a 302 and 5 lug conversion and rolled/pulled wheel wells. On the rear I have been running 245/45/16 on BBS 16X8" wheels with 38mm offset with no problems. In front, 225/45/16 due to bumper clearance issues. I'm not sure if I tried the 245/45 up front but it probably would work with the right trimming or maybe a small spacer.
In the past I have tried several different combinations, up to a max of 235/45/17 front and 245/40/17 rear, on 17X9 chrome GT500 wheels with 24mm offset. That was a particularly heavy combination, but you don't see that stance too often on a Miata.
Mike
https://www.v8miata.net/members/cvx_..._20-miatas-52/
In the past I have tried several different combinations, up to a max of 235/45/17 front and 245/40/17 rear, on 17X9 chrome GT500 wheels with 24mm offset. That was a particularly heavy combination, but you don't see that stance too often on a Miata.
Mike
https://www.v8miata.net/members/cvx_..._20-miatas-52/
Last edited by cvx_20; 06-20-2013 at 02:37 PM. Reason: Added pics
06-20-2013, 07:49 PM
#6
V8 Miata Noob
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My fenders are not rolled and I don't trust myself doing it. If you are in IN and could help I would, but I doubt that.
I guess my NA is stuck with 15" wheels. My main concern is daily driving. I am not racing or doing auto-X at least not yet. So i wount need 17". 16" wheels are a little too tight. It is unfortunate because my rear is a 16" and it will continue to look goofy until I can afford to replace the rear axle with an IRS in a year or two. Just an excuse to burn up the Cooper rs3 I have on the rear I guess.
Thank you all for the clarification. There is just so much out there that figuring out what is best for an individual proves more difficult than I would have thought. I'll post up what I get when I decide... Now for another choice
I guess my NA is stuck with 15" wheels. My main concern is daily driving. I am not racing or doing auto-X at least not yet. So i wount need 17". 16" wheels are a little too tight. It is unfortunate because my rear is a 16" and it will continue to look goofy until I can afford to replace the rear axle with an IRS in a year or two. Just an excuse to burn up the Cooper rs3 I have on the rear I guess.
Thank you all for the clarification. There is just so much out there that figuring out what is best for an individual proves more difficult than I would have thought. I'll post up what I get when I decide... Now for another choice
06-21-2013, 08:24 AM
#7
Jim Stainer
Take a quick road trip to MN and I'll do them for ya!! Miata fenders roll like a dream. There is a bunch of DIY ways to do it or rent a proper roller but I just want to encourage you not to be afraid to roll them yourself. There really is nothing to it and the worst that could happen is you would crack the paint at the edge.
Usually I use a baseball bat or 3 1/2 piece of exhaust pipe but when I did my miata I just grabbed a hammer and went for it. Straight up I have rolled dozens of cars and the Miata was the easiest I've ever done. 65 mustang was the worst, actual metal in that car!
No matter what method you use the trick is to go very slow with it. With a hammer do a million tiny taps to work the metal not just bend it. With a roller or bat add a tiny bit of pressure with each pass. Usually I try to make the transition from straight to rolled gradual over about 4 inches but the metal in the Miata is so soft I don't think it really matters. Keep the paint nice and warm with a hair dryer and if it starts to crack you have gone far enough. Pix of mine are here:
Jim and Jenna build diary, Miata LS1 Conversion: The other half of the back half
You can see how the paint cracked but I did not heat them up or do anything to try and avoid cracking it cuz I'm going to paint the car hopefully this summer. Also you would not have to roll them as far as I did to gain a good amount of clearance.
Usually I use a baseball bat or 3 1/2 piece of exhaust pipe but when I did my miata I just grabbed a hammer and went for it. Straight up I have rolled dozens of cars and the Miata was the easiest I've ever done. 65 mustang was the worst, actual metal in that car!
No matter what method you use the trick is to go very slow with it. With a hammer do a million tiny taps to work the metal not just bend it. With a roller or bat add a tiny bit of pressure with each pass. Usually I try to make the transition from straight to rolled gradual over about 4 inches but the metal in the Miata is so soft I don't think it really matters. Keep the paint nice and warm with a hair dryer and if it starts to crack you have gone far enough. Pix of mine are here:
Jim and Jenna build diary, Miata LS1 Conversion: The other half of the back half
You can see how the paint cracked but I did not heat them up or do anything to try and avoid cracking it cuz I'm going to paint the car hopefully this summer. Also you would not have to roll them as far as I did to gain a good amount of clearance.
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