Pirelli? Schmirelli!

[opelbits]

Many years ago, around '99, I bought a set of Pirelli P600's for the GT. Since I had the 14x6 MSW wheels, I figured I'd use them and got 195/60/14 tires.

The first thing I noticed was how easy it was to slide the car around...too easy. And in the wet, I could get it slide around without even thinking about it. Actually, I was usually thinking about NOT sliding around, but the tires know better than me, right?

Anyway, 8 years later, maybe 15-20k miles, the right front tire started separating. I had noticed some cracks forming from dry rot, so this was not unexpected.

I have had some trouble finding tires I like in a suitable size. My personal preference is for a tire with great rain and snow characteristics and decent dry weather performance. I have never been too concerned with ultimate dry weather performance if it means I can't drive in the wet. I have no use for a two or three season car.

After doing some thinking, I decided to go back to my 13x5 Manta wheels with 185/70/13 tires. The size always seemed to compliment the Manta so well that I figured I try it again on the GT. I have had some questions about the MSW wheels size and offset maybe not being right for the car as the handling sometimes seemed..odd. One of those things that you can't quite put your finger on.

So, I settled on some Kumho Touring A/S 795's. Not a performance tire, per se. I have some really good experiences with Kumho on the Focus, the Safari Van, and the RX7. Tread life is never what it is claimed to be (but you have to look at who is doing the driving!), but the dynamics of the tires has proved to be exceptional, even in the wet.

I put the tires and Manta wheels on the car today. Sure looks different. This will take some getting used to after looking at the MSWs and wide flat Pirellis.

I put 25 miles or so on the car. I can't say anything about the wet weather dynamics since it is sunny and 80. The car feels like it leans more, which is to be expected, given the size and aspect ratio change.
But the biggest change, and a great big surprise, is how quiet they are. The GT was always so noisy. I switched from the seven blade fan to the five awhile back to reduce the noise level. It helped a little. What I realised today was that most of the noise was from my Pirellis. Mostly from the tires themselves, but there is a substantial reduction in the vibration and harshness. I think the Pirellis were transfering alot of road vibration/noise thru the chassis. Probably due to the shorter, stiffer sidewall. Or maybe the treadblock design.
The reviews I read on Tirerack.com (where I get my tires) almost always talked about how quiet the Kumho 795s are, even when compared against other tires of the same size/aspect. I didn't expect such a dramatic change.

To sum it up, I think they will make nice tires for anyone with a stock size wheel. They don't have whitewalls or raised white letters and the tread width looks a little narrow, but if you want a decent tire, these might be just the thing. Especially at $40 per tire ($190 delivered to a local shop, plus $58 for mounting and balancing). We'll just have to see about the rain, though.

I run '75 brakes on the front and I know there are some fitment problems with early wheels. I thought that the Manta style 13x5 wheel (argent rim and spokes with black) was supposed to be okay with the big brakes. Apparently, I was wrong. But a little help from the 4" grinder fairy solved that problem. had to take about 3/16" off the caliper right by the end of the caliper bolts. Funny thing is, I tried my spare on (stock GT wheel) and it also clears the caliper.

Now...can I stand waiting until my new '75 Brembo rotors come in? Then some new calipers and some new drums....you can't polish a turd, but you can make it start and stop faster.

Maybe I shouldn't have said that...

[baz]

you got 15K out of a p600 , i never got more than 6K out of a set , you must drive like a p****

ha ha

well they are not a quiet or hard wearing tyre for sure , it surprises me that you say they slide around a lot as they give up long life for grip (never use P7's they would twist a gt )

"I run '75 brakes on the front and I know there are some fitment problems with early wheels. I thought that the Manta style 13x5 wheel (argent rim and spokes with black) was supposed to be okay with the big brakes. Apparently,I was wrong. But a little help from the 4" grinder fairy solved that problem. had to take about 3/16" off the caliper right by the end of the caliper bolts. Funny thing is, I tried my spare on (stock GT wheel) and it also clears the caliper."

some thing in that paragraph makes me cringe

[Gumby]

EEK I wonder how thick that metal was to begin with?!?

[Lindsay]

Originally Posted by opelbits <snip> I run '75 brakes on the front and I know there are some fitment problems with early wheels. I thought that the Manta style 13x5 wheel (argent rim and spokes with black) was supposed to be okay with the big brakes. Apparently, I was wrong. But a little help from the 4" grinder fairy solved that problem. had to take about 3/16" off the caliper right by the end of the caliper bolts. Funny thing is, I tried my spare on (stock GT wheel) and it also clears the caliper. Now...can I stand waiting until my new '75 Brembo rotors come in? Then some new calipers and some new drums....you can't polish a turd, but you can make it start and stop faster. Maybe I shouldn't have said that...

Interesting ... how much of 75 Big Brake Caliper that needed grinding with Stock 13" wheels. Not sure if SOMEDAY I want to use 1972 GT wheels, but with modified wider rims for 185/70 R13 tires. So, I hesitated on the 75 brake upgrade. Currently using Michelin 185/70 R13 tires ($220 few years ago during COSTCO SALE) mounted on aluminum wheels.

Are 73 GT (agent w/ black) wheels same as 1975 Manta?

[kwilford]

Originally Posted by opelbits I run '75 brakes on the front and I know there are some fitment problems with early wheels. I thought that the Manta style 13x5 wheel (argent rim and spokes with black) was supposed to be okay with the big brakes. Apparently, I was wrong. But a little help from the 4" grinder fairy solved that problem. had to take about 3/16" off the caliper right by the end of the caliper bolts. Funny thing is, I tried my spare on (stock GT wheel) and it also clears the caliper..

The '75 Ascona and Manta rims which fit the bigger brakes are 13 x 5 1/2J, and are easily identified by having the double slot as seen in the thread:
http://www.opelgt.com/forums/3d-whee...k-gt-13-a.html
I wouldn't have tried grinding the caliper, as there is no way to know how close you are to the internal passageways, not to mention the concern of simply weakening the caliper. But if it works, great, just don't grind any more away

[kwilford]

Originally Posted by Lindsay Are 73 GT (agent w/ black) wheels same as 1975 Manta?

Nope, see above

[opelbits]

Hee-hee-hee!

And I thought the last couple of lines would get some remarks...

In order:

baz can bite me! Well, not really, but his insinuation that I drive like a nanny pushing a pram...about what I'd expect from a *former* mod....(just kidding!)

I was always particular about my tire pressure and alignment. I think that helped with wear, but I did drive hard. They did grip well, but it was always easy to overcome that grip. Lesser tires (BF Goodrich comes to mind) would probably be even worse. Perhaps I am driving harder than I thought I was.
Even so, I was surprised by the life of the tires. I'll take pics of them sometime.

As for the grinding...

The grinding was done above the bolts holding the caliper halves together. It was at 45 degree angle in relation to the bolts, just to knock the corner off the caliper, a basic chamfer. I made sure of two things, I went no further back or down than the very ends of the bolts (did not touch the ends of the bolts, either). The other is to make sure you have a consistent width and angle of the grind. This means you are taking off a consistent amount of material, not more in one area than another.

Tis a delicate thing, and not done lightly. rather it should be done very lightly.

This leaves about an 1/8"-3/16" (3mm-4mm for Baz) between the wheel and the caliper at the point of interference. To be clear, it was not the rim that was the problem, but the rear most areas of the wheel spider/face where it is welded to the rim. The very edges of the portions bent back to create that surface/flange were rubbing on the upper outside corner of the caliper. I did not grind 3/16" off an entire side. Why, that would be...stupid?

If I had to do anymore than I did, I would not have done it. As I recall, having taken a caliper apart before (don't worry, I never reused it!), the passages are a little ways from where I was grinding.

kwilford-
I do have a set of the 75 wheels. The misfire in my brain was thinking that somewhere I had read that the similar style earlier wheels would also work and never double checking. Let's just say I was not real happy when I felt the wheel rub.
But now this has me wondering about the earlier wheels. I like the idea of the round hole GT/Kadette wheels, widened and maybe on a 14" rim, no caps or trim rings. But I like bigger brakes too.



All silliness aside, I appreciate the concern for my action. It would be a sad place indeed if questionable actions were not questioned on this website. God knows the things I've heard people attempt on the RX7 board may have had some role in turning a few of my hairs white. Like removing springs from a strut without a spring compressor. "Just back the nut off and stay out of the way"....

I will post pics of the work I did, so there is no confusion.

[opelbits]

Okay, first we had the 'tell', now it's time for 'show'...

The first pic is of the new tires and the 74 Manta wheels. Quite a bit different from the MSW/Pirelli combination.

The second is of the offending lip on the back of the wheel.

The third is a shot thru the slot in the wheel to show (hopefully) what it look like after the grinding.

[opelbits]

And here are pics of the caliper after grinding.

[opelbits]

One concern I do still have, but will be checking soon, is the clearance between the rim and the furthest most point of the caliper. If it is too tight and if the wheel distorts when I hit a big pothole or something (steel has some resilience and could be distorted by an impact, then spring back to it's original shape), then there may be a chance of the rim contacting the caliper. This would obviously be bad.

I do have about 25 miles on the tires already. There has been no sign anything amiss yet.

But this may change.