[jan alma]

I recently decided to switch from original to aftermarket wheels. Im planning to go to 15*50*205

now some people that have driven opel gt`s in the past told me that the handling of the car will decrease dramatically... first because of the wider tires which makes steering harder and second because of the lower `shock absorbing capacaty` of the flatter tire.
these two factors make that where I live (the netherlands) on little country roads with stones in stead of asphalt the car becomes unmanageable according to some...

so tell me, what are your experiences? do i need to adjust my suspension if I go to bigger rims and wider tires? or does this problem not occur...

 

[RallyBob]

This is true to some degree. By increasing the wheel diameter 2", but retaining the same overall tire diameter, you have reduced the effective 'cushion' of air by 2". So this alters the 'spring' rate that the original tires offered.

Also, if you buy tires with a higher speed (VR or ZR or WR) rating than that which the GT came with originally, the sidewall construction tends to be heavier to deal with the increased loads and heat, making the ride stiffer still. And the physical weight of the larger wheel and tire combination will increase unsprung weight, which will react more harshly with impacts (holes) and imperfections in the road. This will require new dampers (shock absorbers) with firmer rebound dampening. This may made the car ride harder too.

Another factor is wheel offset and width. You may inadvertantly alter the scrub radius , which will make the steering feel heavier. Add to this the wider tire and likely grippier rubber compound, and the effort will increase more.

So, yes, it seems that many of the things you fear may come true, but because of the many factors involved it may not be as bad as perceived or in fact it may be worse. This depends on the many items I mentioned above.

I hope this has helped.

 

[gtzero]

Hi Jan,

I've gone from stock to 15s and then to 17s. And I'll share what I've noticed along the way.

Stock is nice but didn't have the look I was after. I went straight to 15s as soon as I got the car and I dropped the suspension. At the time, I didn't know about Opels so I just had them cut the rear coils and re-arc the front springs.

The combination of the 15s and the lowered ride height made a drastic transformation in the ride and handling of the GT. I bought BBS wheels which are definitely lighter than the stock steel wheels. The ride was very smooth and not very harsh over bumps. And with 205s in front and 225s in rear, the car gripped like nobody's business. I'd harass 911s all day long. (My buddy had a 911).

Now I've gone to 17s. Keeping up with the Jones. The ride has gotten quite harsh but the grip is still just as phenomenal. My current 17 inch wheels weigh as much as the stock 13 inch wheels at 17lbs. But the weight of the tires are considerably heavier than stock tires.

If I had to do all over again, I might just stay with the 15s. I think it is the best compromise between ride, handling and looks. (oh, and price). But then again, I love the look of the 17s! Size matters.

It just depends on what matters to you. Have fun with your car.

Manny

 

[opeldean]

re-arc

Hi Jan,

I just had them cut the rear coils and re-arc the front springs.

Manny

what do you mean re-arc springs.

do you want to sell your 15's?

 

[kmon]

rearc'ing springs is just like it sounds. They can change the arc on the leaf spring(s) to either lower or raise the car or otherwise change spring dynamics.

 

[gtzero]

Sorry Bucky,

I had the 15s 20 years ago. I've had 17s on my car for 10years now.

 

[gtzero]

I forgot to mention one more thing.

Grip is great with the new, wide sticky tires. But I will always remember being able to get my GT into a 4 wheel drift prior to getting these big wheels and tires. It was a blast. Now with the new tires, you can grip until you can't grip no more and the tail snaps around. It's not as progressive as before. You really have to anticipate it to catch it. I've yet to re-experience the thrill of 4 wheel drifting, even out on an empty lot with lots of space.

Maybe I just need more practice.

 

[baz]

But I will always remember being able to get my GT into a 4 wheel drift prior to getting these big wheels and tires. It was a blast. Now with the new tires, you can grip until you can't grip no more and the tail snaps around. It's not as progressive as before. You really have to anticipate it to catch it. I've yet to re-experience the thrill of 4 wheel drifting

gtzero when you have more grip and want to 4 wheel drift then you will have to spend your pennys and get more power
wider tires = more traction
power = broken traction
therefore more power+ more traction = faster drifting=

 

[gtzero]

gtzero when you have more grip and want to 4 wheel drift then you will have to spend your pennys and get more power
wider tires = more traction
power = broken traction
therefore more power+ more traction = faster drifting=

That's why I was asking about the height of an SR20DET.

 

[GTJIM (R.I.P.)]

a Better Mouse Trap!

Was going to say: "Forget the SR20DET and go back to 15-inch wheels"

But the answer is simple - just build a better "Mouse trap" - something that will wup small block Chevy Corvettes!

Then Bob comes up with better "Rat Trap" - some thng that will wup Tri-power BIG - block Corvettes!

Gee

 

[gtzero]

Well Manny, it's almost more my engine than my friend's. I'm designing/building it, he's paying for it!

It's a 2.4 bored out to 2.5 litres, with 8.7:1 compression custom Venolias that have been ceramic coated, H-11 tool steel pins, Total Seal rings, ARP rod bolts, polished/shotpeened/balanced rods, o-ringed block, copper head gasket.

The head is also a 2.4 head, with 1.94" intake and 1.60" exhaust valves and pretty much 'maximum' porting. It has titanium retainers, a 'mild' roller cam, roller rockers, a stud girdle, diesel oil pump cover with extended gears, a custom fabricated turbo header, custom fabricated intake manifold, 70 mm throttle body, TEC-2 programmable EFI and ignition, Turbosmart wastegate, Forge blow-off valve, custom Swedish-built intercooler, and a ball-bearing Garrett GT30R turbocharger.

The only things that are not completed at this time are the manifolds, and the turbo still needs to be ordered. But all the hard parts are ready to go together. It'll also have a Getrag 265 tranny and a 3.91 Toyota truck rear axle, plus an aluminum flywheel and S-10 clutch. I will definitely have progress reports as it commences....

I can't seem to stop drooling!

 

[jan alma]

ok, thanks everybody for the advise..

I decided Im going to 15`s. I found bbs rs001 rims that are 15*7 et 25. will these fit? i need to know for sure before im spending all my money on them!

jan