Rear Springs - car with OSS

mjsbrabus

A2OC Donor
Putting some new Bilstien rear shocks on my car and in two minds whether to do the springs at the same time - existing ones are not too rusty.

My question is that there are lots of makes of springs available and some manufacturers differentiate between springs for OSS and non-OSS cars while others do not.

I fully understand why a diesel car - for example - needs uprated springs on the front (due to the significantly heavier engine).

I am thinking, yes the OSS is heavier than the Aluminium roof, but is it that much heavier that it really needs different springs on the back? Or was this a case of Audi 'over-engineering'?
 
I know what you mean. I was looking at the rear springs on my petrol breaker with OSS vs. the ones on my diesel Crystal Blue without OSS. They had different colour codes on them so I didn't swap them, I suppose the OSS ones are in the next heavier-duty class. But then I found out at first hand that the OSS isn't that heavy in the grand scheme of things, you only need two people to lift it because of its size, not its weight. So I like you I do wonder how necessary the stiffer springs actually are. I may yet swap the springs over to at least test them before I send the breaker over the weighbridge.
 
MJS- my study of the relative spring rates last year showed that the aftermarket springs annotated for OSS across the range of ones available (sport and non sport) were essentially scattered across the range so the minor differences were essentially meaningless. Although they made great play of grams here and there for each and every option, to be honest unless your springs are obviously tired / corroded / cracked, replacing the shocks with new ones and replacing the rubbers and mounts at either end of the spring to make sure those are like they were from the factory would probably make more sense and have more effect - and less likely to have an adverse effect by choosing the wrong spring. Obviously if you do decide to change springs, look out for sport vs non sport in terms of height and in some cases higher spring rate.
 
Putting some new Bilstien rear shocks on my car and in two minds whether to do the springs at the same time - existing ones are not too rusty.

My question is that there are lots of makes of springs available and some manufacturers differentiate between springs for OSS and non-OSS cars while others do not.

I fully understand why a diesel car - for example - needs uprated springs on the front (due to the significantly heavier engine).

I am thinking, yes the OSS is heavier than the Aluminium roof, but is it that much heavier that it really needs different springs on the back? Or was this a case of Audi 'over-engineering'?

One of the theories on stiffer springs with OSS is the weight is high up. The increased spring rate is likely not just to compensate for the few Kg extra weight of the roof but mainly to control body roll during cornering.

More info on spring selection with OSS here -

Cheers Spike
 
One of the theories on stiffer springs with OSS is the weight is high up. The increased spring rate is likely not just to compensate for the few Kg extra weight of the roof but mainly to control body roll during cornering.

More info on spring selection with OSS here -

Cheers Spike

Yes, exactly what you have said. Extra weight up top is the worst place for it, so any extra weight in that region needs compensating for. It's the basic law of physics requiring stiffer springs to prevent too much body roll and as the A2 is quite a high car a must for safety reasons.
 
Interesting. Yes I follow the 'extra weight high up' physics - but that weight is not all concentrated on the back end of the car is it. And I don't drive like Lewis Hamilton so body roll / centres of gravity are not major considerations....

One of the existing springs has the fancy Audi colour codes and the other does not so I am guessing that the one that does not is 'aftermarket' and could in fact be anything.

Ribin Cox - noted your comments and yes I'll replace the spring seats (which have virtually disappeared at the bottom). I am sure the new shocks and spring seats will make a big difference - the resistance in the shocks that came off was minimal. They may even have been the originals.

Thanks to all for your input.

Mike
 
Mike,
I've got non OSS Bilsteins on mine, and it's brilliant. I've never had any problems with them and the ride is superb compared to what was on there before. Interestingly enough, I don't see as many OSS front springs as I do rear ones.
Thanks,

Adam
 
Well having looked at the springs Adam I am going to stick with them and just put my new Bilstein shocks on. I am sure it will be much better!
 
Well having looked at the springs Adam I am going to stick with them and just put my new Bilstein shocks on. I am sure it will be much better!

My Blue tdi non oss is lowered 25mm or so and my red tdi with oss standard springs with rear anti roll bar fitted has significant less roll in corners than my lowered tdi. Any one considering buying they are worth every penny

Ross
 
Back
Top