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murph1379:

Why would the Kumhos be any different than the Hoosiers? If anything I'd think the Hoosiers would be harder, since they're wider.  

As was already stated about the beads being different.  The problem is not so much getting the tire on the rim but getting it to bead up is the major PITA.  The sidewalls are so stiff on the Kuhmo that they just buckle and you almost can't push enough air into the tire to get it to bead up.  I have found that 285/30/18 Hoosiers are easier to mount on a 7.5 inch wheel than the 245/35/18 Kuhmos are to mount on the same wheel. 

murph1379:

You know they were calling me Matt Murray over the speaker at Nationals? The announcer thought you were having an especially bad day. =]-Matt Murphy 

Dude, you were definitely dissed. People have been shot for less. I've ruffled WAY too many feathers. You're due for a name change, or run in another class or something. Geeze.....

bob clark:

Todd and I both tried the 275 kumhos and the rubbed a bit but we lived with it. Bigger concern was that they are a considerably taller tire and for my taste the 330 is geared to tall already.

To clarify, you ran Kumho 275/40/17's all around and they fit?

They seem to be the same diameter as the 245/45/17, which I used at the beginning of last season. The shorter Hoosiers were better, but it wasn't a huge difference, IMO.

I ask because I'm considering trying the 275 Hoosiers all around, which have a listed section width skinnier than the 275 Kumho's, or the 265 BFG R1's mentioned by CSBM5, which seems to indicate they'll very slightly rub or not rub at all.

Or maybe I'll give the 275F/245R hoosier combo a try. I would have the gearing of the 245's, but the front grip of the 275's... the big loss is the ability to rotate them if the fronts are still wearing like crazy.

Anyway, your input would be appreciated.

Matt
 

On my 330 I experienced some rubbing at the rear.  I ran the tires on non stock offset wheels at local events where no one cared so I can't say what the rubbing would be like on proper wheels.  Todd ran them on his stock wheels of his 325is.  The first used set he tried he filed down the tread to stop the rubbing he said it made no difference in the handling.  Subsequently he made some spacers which eliminated most if not all the rubbing. The spacers were less than 5 mm.  I have one good set of the 275 Kumhos sitting in the warehouse.  I wonder if I should buy another pair.  They look huge next to the 245 18 Kumhos.  The extra grip might be worth the poor gearing.  Todd does well with his 325is.  Interestingly we once compared cars with the same tires and had 2 national champions drive the cars as well.  The universal response was that his car turned much better but definitely more power on tap in the 330.  Todd's car is totally stock with some mild alignment. My car felt better in stock form too but wheelspin made it much slower. Todd gets wheelspin but not as bad perhaps because of the lower power. 

BadBrad:

Let me know if anything is incorrect or incomplete. 

 

1. Wheels/Tires

·        Wheel notes:

o       SSR GT2 wheels came in stock sizes, but no longer available

o       Most 18x8 wheels have +40mm offset, which is 0.7mm beyond legal limit.

§         Some folks machine off the 0.7mm extra to be legal

 

 

BadBrad - your note about the SSR GT2's coming in stock sizes is not completely accurate - the diameters (18), widths (8.0 & 8.5), and rear offset are stock class legal, but the GT2 front wheel offset is ET40, which is (barely) illegal.  It actually/also falls into the "Most 18 x 8 wheels have +40  offset" category you mentioned above. 

quik96m3:

BadBrad:

Let me know if anything is incorrect or incomplete. 

 

1. Wheels/Tires

·        Wheel notes:

o       SSR GT2 wheels came in stock sizes, but no longer available

o       Most 18x8 wheels have +40mm offset, which is 0.7mm beyond legal limit.

§         Some folks machine off the 0.7mm extra to be legal

 

 

BadBrad - your note about the SSR GT2's coming in stock sizes is not completely accurate - the diameters (18), widths (8.0 & 8.5), and rear offset are stock class legal, but the GT2 front wheel offset is ET40, which is (barely) illegal.  It actually/also falls into the "Most 18 x 8 wheels have +40  offset" category you mentioned above. 

Yeah, I learned that after I posted that list.

 I autoxed my '04 ZHP sedan for the first time yesterday.  Everything is still stock except for the Kumho V710 245/35-18 tires.  I did knock out the front upper strut locator pins to gain some camber, but I think I'm still only getting about -1 degree up front.  Front toe is about zero, and I didn't touch the rear alignment, which had just a little bit of toe-in (~1/16" total).  I'm still trying to figure out tire pressures.  I started at 40f/35r and ended up around 37f/34r, but still not sure which way to go.  Any suggestions?

Rear wheelspin was really annoying.  The course had an uphill start with some offsets, and I felt like the AWD cars gained seconds on me before the second gate.  When powering through turns I was spinning the inside rear tire severely.  The car was very good in high speed transitions, especially for a big heavy sedan (I have been autoxing Miatas for the last several years), but it really pushed in the sweepers.  It's hard to rotate the car, even using lift-throttle or trail-braking.

My next step will be to install a bigger front swaybar.  I hope this will lessen the wheelspin problem without causing much more understeer in the sweepers.  No budget for shocks right now.

BB

BadBrad:

My next step will be to install a bigger front swaybar.  I hope this will lessen the wheelspin problem without causing much more understeer in the sweepers.  No budget for shocks right now.

A bigger front bar is easily the best thing you can do for your set-up, will make a major improvement in front & rear grip and tire wear.  A bigger front bar actually decrease understeer by loading the front tires more evenly (reducing sway increases front tire contact patch when turning by decreasing negative camber loss resulting from body roll). 

Any recommendations on tire pressures for the V710s on this car?

Has anyone ever tried the E90s?  I'm just wondering how competitive they can be?

so, I did some experimenting with 275's up front, and I thought I'd update here.

When I first tried the 275's up front on my sport wheels, at 40psi all around, it was pretty awful. Sweeper grip was clearly improved, but turn in response was non-existent, it would take like half a second. I couldn't get closer than a foot from every cone. increasing front compression a bit and increasing the front tire pressure to 48 helped, but it still felt like I would have been faster on 245's. Increasing the pressure also hurt some of the sweeper grip that had been gained.

I went to Milwaukee last weekend and talked with Bob and Todd down there a bit, and gave the 275's another shot, this time with even higher pressure, around 52. That felt better, and the times were looking pretty good. So for the afternoon runs I swapped to the 245, and right off the bat, I could tell they were still clearly better in transitional response. I still gave up a bit in the sweepers, but with the high pressures, the sweeper performance was pretty close between the 275's and 245's, but the slalom and offset performance was better with the 245's.

I'm going to continue to test, but so far it looks like the 245's are the winner. I think the 275's may wear better, and that might make them worth running, but I have a good 15-20 runs before that will be clear.
 

just an update to this, more testing, 245's still faster.

I'm running 245's this weekend. 

I'm buying a used set of 275 Kumhos, they're older, but I'm mainly interested to see what the transitional response is like, I think they may be better with super wide tires for the wheels, due to the stiffer sidewalls, but we shall see. 

Also, spherical endlinks need to be greased. Lithium spray, then sealed with lithium grease. That was new to me, so I thought I'd include it here. When they're not lubed you get the endlink clunking that I'm sure most of us are familiar with. 

Murph, thanks for sharing your testing info.  I've been running the 245/35-18 Kumhos on my ZHP sedan and they are working pretty well.  I've thought about trying 275s up front, but it sounds like it probably won't help me.  I chose the 245s over 275s in the first place mainly because of gearing -- the 275s are 0.8" taller.

If you are used to Hoosiers, you'll find that turn-in and transitional response will be worse with the Kumhos.  I love the quick turn-in and feel of the Hoosiers -- I feel like I can drive a more precise line with them.  The Kumhos are slower to respond and have higher slip angles.  However, I decided on the Kumhos because I was afraid of cording the outside edge of Hoosiers with my limited front camber.  With Kumhos you'll probably want to add some more front toe-out to help turn-in response.

I have the H&R front swaybar on the stiff setting, which really helped limit rear wheelspin in turns and also helped front end bite a little.  I still have the stock endlinks, shocks, and exhaust, though.  Last weekend I noticed that when I torque my front wheel bolts the wheel moves fore/aft quite a bit, so I suspect that my control arm bushings are worn out.

It's been my experience that spherical endlinks clunk when they're undersized for the application or they don't have sufficient misalignment built in for the application.  All it takes is one bit of interference and the endlinks are toast.  BMW applications need a lot of misalignment tolerance.  Ground Control endlinks at least in the past were woefully deficient on both fronts.

John V:

It's been my experience that spherical endlinks clunk when they're undersized for the application or they don't have sufficient misalignment built in for the application.  All it takes is one bit of interference and the endlinks are toast.  BMW applications need a lot of misalignment tolerance.  Ground Control endlinks at least in the past were woefully deficient on both fronts.

Thanks for the info, what do you mean by misalignment tolerance? Also, do you know of another adjustable endlink that might work better? I've been thinking about trying the Turner Motorsport ones here:

http://www.turnermotorsport.com/html/show_category.asp?txtsearchParamCat=suspwheels#SwayBarParts

They look like they have the advantages of the GC endlinks, but with boots to keep the junk out. (lithium grease all over your tools and hands is rather annoying even if it isn't clunking)

BadBrad:

I've been running the 245/35-18 Kumhos on my ZHP sedan and they are working pretty well. 

While driving a ZHP last weekend I was convinced the steering rack was nearly worth the several thousand extra the ZHP costs, but this I think might make it worthwhile as well. (being able to run the kumhos without the gearing disadvantage)

I have the H&R front swaybar on the stiff setting, which really helped limit rear wheelspin in turns and also helped front end bite a little.  I still have the stock endlinks, shocks, and exhaust, though.  Last weekend I noticed that when I torque my front wheel bolts the wheel moves fore/aft quite a bit, so I suspect that my control arm bushings are worn out.

I just replaced all my bushings (70k) and it tightened everything up considerably, wish I'd done it a year ago! 

I keep meaning to try the bar on the stiffer setting and I keep not doing it, maybe that's going to have to make it into the Milwaukee TnT. I wish I'd actually tested and tuned at ours... doh. 

murph1379:

John V:

It's been my experience that spherical endlinks clunk when they're undersized for the application or they don't have sufficient misalignment built in for the application.  All it takes is one bit of interference and the endlinks are toast.  BMW applications need a lot of misalignment tolerance.  Ground Control endlinks at least in the past were woefully deficient on both fronts.

Thanks for the info, what do you mean by misalignment tolerance? Also, do you know of another adjustable endlink that might work better? I've been thinking about trying the Turner Motorsport ones here:

http://www.turnermotorsport.com/html/show_category.asp?txtsearchParamCat=suspwheels#SwayBarParts

They look like they have the advantages of the GC endlinks, but with boots to keep the junk out. (lithium grease all over your tools and hands is rather annoying even if it isn't clunking)

By misalignment I mean the number of degrees the "ball" can move relative to the housing before something binds up.  This could be the bolt hitting the housing, or the flange on the ball hitting the housing, it depends.  You need a lot of misalignment on a BMW because the cars have so much suspension and steering travel.  If you're careful to set the links so they're centered at normal ride height I guarantee they will bind at full compression or droop with some steering angle if you have the GC endlinks. 

The ones on my car are massively oversized for the application in terms of load, but it was done that way so they wouldn't bind up.  And they don't.