New wheels = no brakes?
 

I recently installed BBS CH-R 19" wheels on my '01 Boxster S. I love the wheels, but I have noticed an alarming problem with them and wonder if there is a solution.

All of a sudden my braking has been greatly reduced. Cruising on the highway, when I need to suddenly brake for traffic, I have to use what seems like twice the leg power and wait for what seems an eternity for the brakes to grab.

The 19" wheels and tires are of course a few pounds heavier than my usual 17" setup. Could that be why my brakes are so slow to grab?

Or is it that the wheels are so much bigger, giving the brakes so much more cooling air, that whenever I want to use them they are "stone cold" and need to warm up a little on application before grabbing?

Or is it a combination of both? Or something else?

That's very odd behavior. Wheels that are a few pounds heavier should not effect a car with this much torque, or clamping force. Do you happen to know the exact weight difference including tires? You've moved more tire mass towards the outside, which at high speed will certainly be harder to bring to a stop, but if little econobox Hondas can run around with 20s all day, I doubt that is your problem.

Did you ensure the tire pressures are not jacked up to 40 lbs like they do at the mounting place? They will also need a few hundred miles to break in. If they are a hard compound, for longevity, it could be just a lack of grip compared to old tires. It's amazing to me when I upgrade tires on cheap non-performance cars how much more effortless the brakes get even at highway speeds. There'a a whole lot of friction going on at any speed. :)

Seems odd. Have you inspected your brake lines? May be time for stainless brake line upgrade? I have 19's on my 98 and braking performance feels the same.

My braking improved from 17-18" wheels. There is a larger contact patch now.

More likely the tires are to blame since they are larger diameter & heavier, increasing the "flywheel effect".

I would think that both are unrelated ==> check your brakes

There's no way wheels & tires caused that problem unless you put Monster Truck tires on it. Did the problem start at the exact same time the new wheels were installed? It could even be a brake booster problem.

Some more details:

Brake fluid is topped up. I flushed and changed to ATE Super Blue LAST spring. No brake problem for about 14 months.

I've got at least 1/4" of pad material (on the outboard pads, anyway). Do the inboard pads wear any faster than the outboard? I would think not.

Never seen any kind of brake-related warning light...I believe I have two, right? One light that would warn me of low brake fluid and one for low pad material?

I went from 17" Michelin Pilot Sport A/S Plus, which were excellent in every way, run from last fall, all winter, until just a few weeks ago. The new 19s are Michelin Pilot Super Sports, which, jeez, should INCREASE my braking power.

It really seems to me that this braking problem did not appear until AFTER I had more than 500 careful miles on the Super Sports, which is nuts!

Being brand-new wheels, with a lot of spokes, I have been cleaning them excessively with a LOT of dilute Simple Green and water. But jeez, I would think any slipperyness from residual Simple Green would be gone after one or two applications of the brakes.

Just before this problem arose, it is true that I did slather Black Magic Tire Wet dressing on the sidewalls, and the design of the Super Sports is such that they have VERY rounded "shoulders," and yeah, I did get some of this stuff on the first inch or so of the outboard shoulders, but...I have driven through a lot of rain since then, and it is hard to believe that the dressing is affecting the contact patch.

I dunno, it's weird. I step on the brakes and it's like nothing happens for a second or two. Then they start to grab. And the grab seems muted, only about half of what I am used to. It's like my pads are "glazed"?

I have to do something about this, though, because I commute on the Merritt Parkway in Connecticut (my own private Nurburgring when I am traveling in the opposite direction of the rush-hour jam), and it is common to go around a curve and suddenly come upon a sea of brakelights from stopped traffic. (This is literally a recurring nightmare I have, ha!) If I am lucky I have 50yds in which to go from 85mph to zero!

I think you have a brake problem. You've got good tires and appropriate wheels. If it was something with the tread surface, it would be affecting cornering as well. Has to be the brake system somewhere.

Brake problem. Put your original wheels back on and test. I'll bet you have the same issue.

Maybe you contaminated you brake pads in some way? Though I don't see how normal cleaners would do that. Pads often don't wear evenly, even on 4-piston calipers, so I would check them. Also check for sticking caliper pistons.

Bleed your brakes again

Must have spent a pretty penny on those CH-Rs... Post pictures

Just a side note, I wouldn't put simple green anywhere near those wheels. Are you diluting the stuff? I suppose it could potentially attack the compound on your brake pads too, but I've not heard about this before. People like to blame stuff on simple green, cause its used so much. It's really powerful though, so anything's possible if you sprayed it all over the affected area. What a stumper, though.

Have you tried braking really hard from speed to a stop? Maybe do that a few times, but overall, I can't think of how switching out wheels would cause this unless you altered the brakes, which if we get real technical, you did with simple green. If those are the only two things you've done, then it probably is one of those two things. If you had just messed with the brake system, I think we'd have a culprit. There's really no way those wheels could be causing THAT much additional effort to stop, especially with the compounds. If in 200 miles its not gone, something is definitely wrong. Some 19" tires are incredibly heavy though. You can increase your mass by a few lbs pretty easy among models, and being all the way to the outside, the effect is more pronounced. This probably shouldn't be underestimated in general when talking about performance, but your symptoms are not bad enough to warrant it as a cause.

+2 brake booster-- and at .25 inch of pad it's time to change them regardless
I wonder if you've got a brakeline anoreysm-usually these burst leaving you with practicly no brakes but maybe you have one that's just swelling under force. That's why I'm installing stainless- I don't want any BIG MOMENTS!!

Yes, the inboard pads can wear differently than the outboard pads (or vice-versa). In a perfect world they should be expected to wear the same but sometimes the world isn't perfect.

You can easily check the outboard and inboard pad thickness without removing the wheels by using a small mirror and a flashlight.

I'm just finishing a brake job on my car and found the pads were within about .010 inch end to end and inner to outer-I was amazed since I'm used to single piston designs which typically have a much wider tolerance.

Thanks
 

Some great ideas here, thanks, guys.

The CH-Rs were not outrageously priced, at least, compared to the cost of fully-forged BBS wheels like the LM or LM-R. My budget just wouldn't stretch that far. They have the advantage of taking OEM center caps, having a replaceable stainless rim protector, and of course, are BBS-quality. I like them a lot, although I would have gone for 18s instead of 19s if they were available.http://986forum.com/forums/uploads01...1369998361.jpg

What size wheels and tires? The tires really look stretched on the rim.

yeah - mebbe mark the rim and tire and see if it's spinning on the rim?