Hi all, recently had my MOT and ends up I have a nail in my rear tyre so I\'m on the hunt for some new ones. Been reading through many threads on multiple forums and I still can\'t figure out what will fit.
Currently the wheels are 18 x 9.5 ET 20 and the previous owner stretched a 225/40 on there, plenty of clearance with that, but I\'m not keen on that big of a stretch and since I\'m replacing anyway I would like the most rubber I can get on the road.
The rear arches aren\'t rolled, and it\'s not on the cards just now, wondering if anyone has any idea what size of tyre I can run without rubbing? I thought about just going with a 235/40 I know it will still be a fair stretch, but not as bad as it was. Does anyone know if a 245 or even a 255 will fit without rubbing?
Essay over, ha ha, sorry for the massive spiel.
subscribed, the previous owner of my car stretched a set of 235`s on my 18`s, not sure the rim sizes but they arey super wide rota drifts.
I dunno why anyone would put small tyres on a powerful rear wheel drive car - its not safe in my opinion, I am looking at 285 toyo 888`s - just need to go to a drift day and destroy these maxxis tyres and then I will be in the market for new treads too - interested to see if I need to do any work to get 285`s on - I have 25 mm eibach spacers already.
Thanks
No it\'s baffling why you would, I\'d never even heard of stretching tyres before I got the FD as I always slapped the most rubber I could on, but there will be clearance issues if I do that with these and I\'m not buying wheels any time soon, so I\'d like to stick wider tyres on. I don\'t have the cash for all new treads, or I would go better, but gonna stick with the Maxis MZ1 just now cos you can get a pair for under £200 new.
This whole " lets stick stretched tires" looks terrible, totally makes the car handle worse as you have zero tire roll. The craze started with the vw boys when I lived in Germany 20years ago . This was because they were slow and they scrapped their way everywhere. In a cool way.
Why the hell anyone would want to ruin a car with such amazing handling is beyond me.
i had 265 40 18 on my rear dropped 30mm and never rubbed touched or otherwise....cant remember the offset though....which i think you need to get write....
Front was more of an issue though going 18\'s had 225 35\'s on there and dropped 30 mm and would occassionally scrub on arch liners.
I dont like the stretched look either.....
265/35/18s fit easy on the rears, no rubbing. Fronts 235/40/18 with a little rubbing, no spacers, just deep dish
Yeah it\'s the offset that\'s confusing me most, et 20 isn\'t too common and I can\'t find a damn thing about that offset and a 9.5" wheel. I know the fronts are et 35 8.5" with 225/40 and no clearance issues.
Thinking I\'ll have to stretch some unfortunately as the wheel sits flush with the outside of the arch so tyres that fitted right would rub. I don\'t mind the stretched look, but it\'s not for show so function over form every time.
Quote from: Grant Monkhouse;855651265/35/18s fit easy on the rears, no rubbing. Fronts 235/40/18 with a little rubbing, no spacers, just deep dish
That\'s good to know, how much does offset effect this? I\'m a total noob when it comes to working these things out, always bought wheels with near oem offset for other cars.
I\'ve got 275 on a 10.5 et 42 no problem with rub
goto //www.rochford.tyres mate excellent guide on there for sizes offset pcd explained....visited it myself quite a few time:yes
link dont work but type in manually....
I have front 235/40 with 18x8.5+32 offset and 265/35 18x9.5+35 on the rears, zero rub on the back and the only rub on the front is the arch liner on full lock. Obviously it depends if you\'re lowered or not too.
Well after having a good look the other night I really do think I\'ll have issues with anything over a 235/40 on the rear with that offset :(
Quote from: Metalorama;855894Well after having a good look the other night I really do think I\'ll have issues with anything over a 235/40 on the rear with that offset :(
I\'m surprised to hear this, for the rear with a 9.5J rim... usually there\'s loads of room.
Are you running stock susp or is it lowered heavily?
for ref: I ran a 255/40/17 on a 9J on the rear et38. Fitted no probs and I had plenty of rooms to spare. Since then, I\'ve bolted on 15mm spacers to the rear, making that et23, sits flush, still no worries, rubbing etc.... Mine runs pretty low at the rear too.
Only diff is, my rear arches are rolled just slightly at the top.
HTH and just for ref, here\'s a pic of mine. 9j + 235/45/17 front, 9J + 255/40/17 rear. Quite low as you can see, no probs at all :)
(https://lh5.googleusercontent.com/-HoT8Y1Db5II/T4mft1FAo1I/AAAAAAAAJeU/RzlV98jeI2U/s1043/2012-04-14+15.02.06.jpg)
9.5" is 240mm so I would thought a 255 tyre with a 35 profile would be ideal. Maybe worth going to a tyre shop and ask them what they recommend. Take the original wheel and tyre size for the rx7 and they will be able to tell you what will work.
The wheel (and hence tyre) is too far out from the hub , the movement is a radius...et 20 is wrong should be 35 offset ideally so under suspension compression the tyre can go up inside arch without catching lip.
Just to show what you can do and what fits, these are 18x10 et20 with 255/35
http://www.flickr.com/photos/johnrenna/5722750998/
Sorry guys, haven\'t had acces to a computer the last few days and my phone was being a dick. The car is quite low, not any lower than yours though fil (those wheels are NICE by the way!) I have read before now that the offsets aren\'t ideal, the wheels look nice, but if I were to buy wheels for it I\'d have gone with something closer to 35.
18x10 255/35 looks just right actually so I should be ok with a 255 then, are the arches rolled at all? Since I\'m running 40 profile on the front would it be retarded to run 35\'s on the rear only? I don\'t have the cash right now to buy 4 tyres but I really need rears.
if you have the same width wheels all round then you need the profiles to be the same, if theyre thinner on the front then you will require a different profile. theres a way to work it out bu i dont know how, but if you run the same profile you end up with the car looking like its leaning forward because the rears are actually bigger in circumference.
i have had 3 people explain to me about why different width tyre/wheel combos require different profiles and i still dont really understand why
Your rears should be fine though, if not a slight roll of the inner ip can be done easily.
It\'s all to do with rolling circumference. That is the distance around the edge of the tyre, or the distance the wheel and tyre will roll if you push it for one revolution.
On a car like the RX7 you need to have the same rolling circumference on all four tyres as otherwise the ABS (if fitted) will think one axle is rotating at a different speed under braking and cause ABS faults under braking. On an RX8 it\'s even more important because of the DSC (b***h switch) as this is calibrated based on identical rolling circumferences on all wheels.
The way to check is the following:
First off you need to know the overall diameter of the tyre and wheel combination.
The wheel is easy, that\'s just the diameter of the rim. So on a 17 inch it\'s 17 inches. (Obvious). However because the imperial system gives me a headache I like to convert it into millimetres. There are 25.4 mm to every inch so a 17 inch rim has a diameter of 17 x 25.4 mm = 431.8 mm
You then need the extra diameter added by the profile of the tyre. Say you\'ve got a 235/40R17 tyre. The profile is a percentage of the width of the tyre, so on a 40 profile tyre the profile is 40% of the width. The width of the tyre is given in mm.
So the profile of the tyre in mm is 235 x 40% (or 0.4) = 94 mm
Because you\'ve got tyre at the top and bottom of the rim you have to multiply that by two.
2 x 94mm = 188mm
Therefore the overall diameter of the tyre is the diameter of the rim + 2 x the size of the profile.
So in the case of our example:
The diameter of the wheel and tyre is:
431.8mm + (2 x 94mm) = 619.8 mm
To get the circumference you simply multiply the diameter by pi. If you\'re doing this on a calculator then use the pi button (π).
619.8 x π = 1947.16 mm
If you want to compare it to a 255/35R17 tyre you need to find the diameter of that tyre.
The rim diameter is the same, 431.8 mm
The tyre profile is 255 x 0.35 = 89.25
Therefore the overall diameter is 431.8 + (89.25 x 2) = 610.3
The rolling circumference is therefore:
610.3 x π = 1917.31 mm
It\'s immediately obvious that the 255/35R17 has a smaller rolling circumference but to find the percentage difference you need to divide the smaller number by the larger number and multiply the result by 100.
1917.31/1947.16 x 100 = 98.46%. The smaller 255/35R17 tyre is 98.46% of the size of the 235/40R17 Tyre. Or it\'s 1.54% smaller. Generally most ABS systems will tolerate a difference of 1-2% so you\'d be okay.
If you don\'t have ABS then it\'s not a problem you just have to fit the same size tyre across the same axle, particularly on the rear if it\'s fitted with an LSD, a difference in size on these will wear out the LSD very quickly.
Quote from: Grant Monkhouse;855998if you have the same width wheels all round then you need the profiles to be the same, if theyre thinner on the front then you will require a different profile. theres a way to work it out bu i dont know how, but if you run the same profile you end up with the car looking like its leaning forward because the rears are actually bigger in circumference.
i have had 3 people explain to me about why different width tyre/wheel combos require different profiles and i still dont really understand why
Your rears should be fine though, if not a slight roll of the inner ip can be done easily.
I was worried that the car might look like it was leaning back with the front sitting higher and just look stupid, I might bite the bullet and go with 35 profile all round. I get confused by the whole thing, that\'s why I thought I\'d best ask before I spend hundreds on unuseable tyres.
Quote from: Will66;855999It\'s all to do with rolling circumference. That is the distance around the edge of the tyre, or the distance the wheel and tyre will roll if you push it for one revolution.
On a car like the RX7 you need to have the same rolling circumference on all four tyres as otherwise the ABS (if fitted) will think one axle is rotating at a different speed under braking and cause ABS faults under braking. On an RX8 it\'s even more important because of the DSC (b***h switch) as this is calibrated based on identical rolling circumferences on all wheels.
The way to check is the following:
First off you need to know the overall diameter of the tyre and wheel combination.
The wheel is easy, that\'s just the diameter of the rim. So on a 17 inch it\'s 17 inches. (Obvious). However because the imperial system gives me a headache I like to convert it into millimetres. There are 25.4 mm to every inch so a 17 inch rim has a diameter of 17 x 25.4 mm = 431.8 mm
You then need the extra diameter added by the profile of the tyre. Say you\'ve got a 235/40R17 tyre. The profile is a percentage of the width of the tyre, so on a 40 profile tyre the profile is 40% of the width. The width of the tyre is given in mm.
So the profile of the tyre in mm is 235 x 40% (or 0.4) = 94 mm
Because you\'ve got tyre at the top and bottom of the rim you have to multiply that by two.
2 x 94mm = 188mm
Therefore the overall diameter of the tyre is the diameter of the rim + 2 x the size of the profile.
So in the case of our example:
The diameter of the wheel and tyre is:
431.8mm + (2 x 94mm) = 619.8 mm
To get the circumference you simply multiply the diameter by pi. If you\'re doing this on a calculator then use the pi button (π).
619.8 x π = 1947.16 mm
If you want to compare it to a 255/35R17 tyre you need to find the diameter of that tyre.
The rim diameter is the same, 431.8 mm
The tyre profile is 255 x 0.35 = 89.25
Therefore the overall diameter is 431.8 + (89.25 x 2) = 610.3
The rolling circumference is therefore:
610.3 x π = 1917.31 mm
It\'s immediately obvious that the 255/35R17 has a smaller rolling circumference but to find the percentage difference you need to divide the smaller number by the larger number and multiply the result by 100.
1917.31/1947.16 x 100 = 98.46%. The smaller 255/35R17 tyre is 98.46% of the size of the 235/40R17 Tyre. Or it\'s 1.54% smaller. Generally most ABS systems will tolerate a difference of 1-2% so you\'d be okay.
If you don\'t have ABS then it\'s not a problem you just have to fit the same size tyre across the same axle, particularly on the rear if it\'s fitted with an LSD, a difference in size on these will wear out the LSD very quickly.
Wow! I had no idea so much was involved. Thanks for the in depth explanation, at first glance I thought my head was going to explode with all the information, but you have broken it down so it is useable for plebs like me, ha ha. Thanks man, really appreciate it :god
Smarty pants award goes to Will. I knew it was about the circumference but that\'s it.
Quote from: Will66;855999It\'s all to do with rolling circumference. That is the distance around the edge of the tyre, or the distance the wheel and tyre will roll if you push it for one revolution.
On a car like the RX7 you need to have the same rolling circumference on all four tyres as otherwise the ABS (if fitted) will think one axle is rotating at a different speed under braking and cause ABS faults under braking. On an RX8 it\'s even more important because of the DSC (b***h switch) as this is calibrated based on identical rolling circumferences on all wheels.
The way to check is the following:
First off you need to know the overall diameter of the tyre and wheel combination.
The wheel is easy, that\'s just the diameter of the rim. So on a 17 inch it\'s 17 inches. (Obvious). However because the imperial system gives me a headache I like to convert it into millimetres. There are 25.4 mm to every inch so a 17 inch rim has a diameter of 17 x 25.4 mm = 431.8 mm
You then need the extra diameter added by the profile of the tyre. Say you\'ve got a 235/40R17 tyre. The profile is a percentage of the width of the tyre, so on a 40 profile tyre the profile is 40% of the width. The width of the tyre is given in mm.
So the profile of the tyre in mm is 235 x 40% (or 0.4) = 94 mm
Because you\'ve got tyre at the top and bottom of the rim you have to multiply that by two.
2 x 94mm = 188mm
Therefore the overall diameter of the tyre is the diameter of the rim + 2 x the size of the profile.
So in the case of our example:
The diameter of the wheel and tyre is:
431.8mm + (2 x 94mm) = 619.8 mm
To get the circumference you simply multiply the diameter by pi. If you\'re doing this on a calculator then use the pi button (π).
619.8 x π = 1947.16 mm
If you want to compare it to a 255/35R17 tyre you need to find the diameter of that tyre.
The rim diameter is the same, 431.8 mm
The tyre profile is 255 x 0.35 = 89.25
Therefore the overall diameter is 431.8 + (89.25 x 2) = 610.3
The rolling circumference is therefore:
610.3 x π = 1917.31 mm
It\'s immediately obvious that the 255/35R17 has a smaller rolling circumference but to find the percentage difference you need to divide the smaller number by the larger number and multiply the result by 100.
1917.31/1947.16 x 100 = 98.46%. The smaller 255/35R17 tyre is 98.46% of the size of the 235/40R17 Tyre. Or it\'s 1.54% smaller. Generally most ABS systems will tolerate a difference of 1-2% so you\'d be okay.
If you don\'t have ABS then it\'s not a problem you just have to fit the same size tyre across the same axle, particularly on the rear if it\'s fitted with an LSD, a difference in size on these will wear out the LSD very quickly.
I did make an excel page that would work it all out for you but unfortunately I lost it when a hard drive died and I haven\'t got round to doing it again. But once you know the maths it\'s not difficult.
I knew it 80 % ...but could not explain that way......top marks!
Nice explanation above but if you want a quick tyre size calculator I\'ve been using one for years. Doesn\'t cover offsets and and rim widths but an easy way to compare % changes to the speedo and overall tyre diameter changes.
Search for Miata Tyre Calculator
PS I\'m a standard alloy fan so I can\'t help with fitting big tyres.