[Oldguysrule]

We know that Michelin Cross Climate 2s AS in 245/40/21 fits the fronts of 21" wheels based on a member's report. Stock size is 240/40/21 so it's about 8 or 9/10" shorter in diameter than the 45 series. Just wondering if anyone else has the taller 45 series in front and if so, what tire and more importantly, what is the clearance between the bottom of the coil and top of the tire? I've asked the member repeatedly to just take a peek and ballpark clearance from bottom of coil to top of tire but I've received no reply.

Reason I ask is the Crossclimate II is about 1/10" lower in diameter than the Pilot Sport 4 AS tire and I was wanting to install that but it's going to be a close fit based on the Bridgestone RF tire I have on their now. I'm currently measuring about a 5/8" clearance with the stock 40 series.
Thanks in advance.

[Oldguysrule]

Where is Zilk3r?
Just need a measurement.

[OciWan]

I am interested in this as well

[mattsheng]

Not sure what you meant by "the clearance between the bottom of the coil and top of the tire". When you say coil do you mean the spring coil on the front strut? The tire-to-strut clearance shouldn't be affected when changing to a higher aspect ratio tire given that the width stays the same.

Changing to a higher aspect ratio tire will decrease the tire-to-wheel-arch clearance though. Since I don't run a 245/45R21 tire, I can't physically measure that clearance for you. But I do have the normal ride height figure and I can calculate the tire-to-wheel-arch clearance for you using simple math.

The normal ride height (A) measured from bottom center of the rim to lower edge of wheel arch is 707mm for 21" wheel G01 LCI/pre-LCI. The diameter of a 21" wheel is of course 21" = 533.4mm (B). So the distance from the top center of the rim to lower edge of wheel arch should be 707 - 533.4 = 173.6mm (C). Distance C = sidewall + tire-to-wheel-arch clearance so tire-to-wheel-arch clearance = C - sidewall. Sidewall for 245/40R21 = 245 * 0.4 = 98mm and that for 245/45R21 is 245 * 0.45 = 110.25mm.

So tire-to-wheel-arch clearance for 245/40R21 is 75.6mm ~ 2.98" and that for 245/45R21 is 63.35mm ~ 2.49". So the clearance decreases by about 0.5". This estimation is, of course, based on the assumption that the sidewall is a constant measure regardless of the tire construction, material, whee rim width, etc. But this should give you a ballpark figure.

[Oldguysrule]

Originally Posted by mattsheng

Not sure what you meant by "the clearance between the bottom of the coil and top of the tire". When you say coil do you mean the spring coil on the front strut? The tire-to-strut clearance shouldn't be affected when changing to a higher aspect ratio tire given that the width stays the same.

Changing to a higher aspect ratio tire will decrease the tire-to-wheel-arch clearance though. Since I don't run a 245/45R21 tire, I can't physically measure that clearance for you. But I do have the normal ride height figure and I can calculate the tire-to-wheel-arch clearance for you using simple math.

The normal ride height (A) measured from bottom center of the rim to lower edge of wheel arch is 707mm for 21" wheel G01 LCI/pre-LCI. The diameter of a 21" wheel is of course 21" = 533.4mm (B). So the distance from the top center of the rim to lower edge of wheel arch should be 707 - 533.4 = 173.6mm (C). Distance C = sidewall + tire-to-wheel-arch clearance so tire-to-wheel-arch clearance = C - sidewall. Sidewall for 245/40R21 = 245 * 0.4 = 98mm and that for 245/45R21 is 245 * 0.45 = 110.25mm.

So tire-to-wheel-arch clearance for 245/40R21 is 75.6mm ~ 2.98" and that for 245/45R21 is 63.35mm ~ 2.49". So the clearance decreases by about 0.5". This estimation is, of course, based on the assumption that the sidewall is a constant measure regardless of the tire construction, material, whee rim width, etc. But this should give you a ballpark figure.
Attachment 3062593

Yes, there is wheel arch clearance enough to run 45 aspect 21" tires. The strut coil clearance concerns me. With a 40 series 21" tire there is maybe 5/8" clearance from top of tire to bottom of strut coil plate. Since 45 series adds almost an inch of tire height, its going to be very close if you halve that. It will depend on tire manufacturer or in this case, model of tire. Crossclimate 2 are a tad shorter than Pilot Sport 4AS based on tire diameter.

[mattsheng]

Originally Posted by Oldguysrule

Yes, there is wheel arch clearance enough to run 45 aspect 21" tires. The strut coil clearance concerns me. With a 40 series 21" tire there is maybe 5/8" clearance from top of tire to bottom of strut coil plate. Since 45 series adds almost an inch of tire height, its going to be very close if you halve that. It will depend on tire manufacturer or in this case, model of tire. Crossclimate 2 are a tad shorter than Pilot Sport 4AS based on tire diameter.

Increasing the aspect ratio shouldn't affect the fitted tire width too much, even if the tire is from a different manufacturer. The larger diameter will decrease the tire-to-strut clearance if the wheel bearing is not parallel to the strut. If you're using the regular/standard steering knuckle, the wheel bearing should be parallel to the strut so increasing the tire diameter shouldn't decrease the tire-to-strut clearance.

Also, there are many folks reporting that running 265/40R21 at the front is fine even though it is 0.8" wider than 245/45R21 or 245/40R21. The diameter of 245/45R21 is only 0.4" larger than that of 265/40R21 anyway so I won't be too concern.

[Oldguysrule]

Originally Posted by mattsheng

Increasing the aspect ratio shouldn't affect the fitted tire width too much, even if the tire is from a different manufacturer. The larger diameter will decrease the tire-to-strut clearance if the wheel bearing is not parallel to the strut. If you're using the regular/standard steering knuckle, the wheel bearing should be parallel to the strut so increasing the tire diameter shouldn't decrease the tire-to-strut clearance.

Also, there are many folks reporting that running 265/40R21 at the front is fine even though it is 0.8" wider than 245/45R21 or 245/40R21. The diameter of 245/45R21 is only 0.4" larger than that of 265/40R21 anyway so I won't be too concern.
Attachment 3062613

Yes but like I said, tire diameter varies a bit based on tread depth, which varies a bit with make and model. The difference in height between 40 series and 45 series is about 1/2". That is about all the room between the current 40 series and the coil now. I'm concerned with height, not width. It will be close.

[Zilk3r]

Ouch! Called me out. We got a ton of snow this week so probably not ideal, but here’s a picture. We’ll have to wait for snow to melt before I can get an accurate measurement, but I’d say it’s pretty damn close as is.

[Oldguysrule]

Originally Posted by Zilk3r

Ouch! Called me out. We got a ton of snow this week so probably not ideal, but here’s a picture. We’ll have to wait for snow to melt before I can get an accurate measurement, but I’d say it’s pretty damn close as is.

Thx! Yes, not much room to spare. A dry pic would be great. I think the Pilot Sport AS are said to be 0.10" taller.

[Zilk3r]

It’s supposed to warm up a ton these next few days. Probably can get a dry pic and measurement by Monday!

[mattsheng]

Originally Posted by Oldguysrule

Thx! Yes, not much room to spare. A dry pic would be great. I think the Pilot Sport AS are said to be 0.10" taller.

Yea, not a lot of room indeed! I thought the bottom of the spring perch is not protruding out too much so a taller tire shouldn't cause issues. But I was wrong! I checked my 21" wheel this morning and saw the spring perch protrudes out so much that a taller tire will definitely rub against the spring perch. I never thought about this clearance issue because I used to run KW on my A3 8V and the spring perch was so small

[climbbike]

Why not just run 255/40 r21 all the way around? That’s what I do with the PILOT SPORT ALL SEASON 4. Handles and tracks WAY better too than with the staggered setup. Back probably breaks loose a little easier but that’s a plus for me.

[Oldguysrule]

Originally Posted by climbbike

Why not just run 255/40 r21 all the way around? That’s what I do with the PILOT SPORT ALL SEASON 4. Handles and tracks WAY better too than with the staggered setup. Back probably breaks loose a little easier but that’s a plus for me.

I'd rather keep the look of 275 in the rear but not have to go 295 cuz that's a little too much for me.

[Oldguysrule]

Pilot Sport AS are 1/10" taller in circ than Crossclimate 2, so 1/20" less clearance from spring perch in a 45 series front. That's not much so they will probably be OK as well.

[Crudowns]

Originally Posted by Zilk3r

Ouch! Called me out. We got a ton of snow this week so probably not ideal, but here’s a picture. We’ll have to wait for snow to melt before I can get an accurate measurement, but I’d say it’s pretty damn close as is.

Is there any way to add more clearance to the shock tower? I would like to add larger diameter (255/50/20) front wheels for my winter setup.

[Oldguysrule]

Probably not feasible without significant expense. You'd need new struts that have a higher spring perch and then you'd need new coils that would be shorter as well. That leaves the dynamics front to back maybe a little out of whack too so then you may need to change out the rears with a matching set from the same mfg.