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Discussion Starter · #1 ·
Why would the bump stops be different for these wheel sizes? The EPC makes a distinction.

I could see a spring eight difference making a difference in the bump stop. But AFAIK, spring sizes were not tied to wheel sizes. They were tied to equipment/weight.

Even if it was tied to wheel size, why would 15" be different from 16/17", but 16" not be different from 17"?
 

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Current: 2000 9-3 Aero 5d, Family: 85 900i 3dr.
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My understanding was the bump stop was different for the Viggen as that had 17” rims whereas all others had 15 or 16”. Does the EPC show that difference at all?
 

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So the 16” and the 17” equate to the aero/SE and the Viggen. These had special springs and struts that were different from the base model. That might explain the bump stop difference in the EPC.
 

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I bought a pair of the 17” bump stops when I put Viggen springs on the back of my 1997 900. There was a difference between the original bump stops and the new ones, but not much. I wish I could reminder the particulars, but I think it was just a difference in the length of the stop itself, the foam part that sticks down in between the coils. The 17” was shorter, I think.
 

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Discussion Starter · #6 ·
Yeah, I thought about it a bit more.

The 15" cars did look to be higher but I always thought it was the smaller wheel and narrow tires. But we all heard the rumors that the SE versions were lower. Unfortunately no one ever documented the actual spring rates for the rear amongst the six colored spring options. As I mentioned, I always thought it was weight / option based or the convertible getting stiffer springs for the added roof weight in the rear when the roof opens.

But approaching it logically, we all know the Viggen was 10mm lower. That was documented by Saab. So it would have had shorter bump stops. The EPC has the 16" and 17" as the same part, so the 16" would also have been shorter. The 15's springs must have been a bit higher with taller bump stops.
 

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They really were. For a while you could get Moog bump stops for quite a bit less from Rock Auto. That’s what I bought, and they ended up being the factory parts with Saab stamped on them and the factory part numbers.
 

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But tire OD is the same for all stock sizes... so isn't it only spring travel that matters? Shorter springs would mean shorter bump stops.
Shortening the bump stop puts the tire deeper into the wheel well at full compression. Whether the spring is shorter or taller doesn't matter... you can only put the tire so deep before contact.

In many if not most situations, people will shave bump stops to make up for shorter springs to maintain travel, but given the, um, underwhelming suspension design on the 9-3 that may not have been possible. Or maybe Saab just didn't want to do it. Who knows?
 

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... also, the first 9-3s had the same 205/50-16 as the NG900, but the later 9-3 had 205/55-16. The former is like a half inch shorter than the Viggen and the latter is a quarter inch taller, so who knows how that affects whatever Saab calculated.
 

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Discussion Starter · #18 ·
My thought is that the wheel will never bottom in the wheel well. They'll engineer that out as a hard stop and the coils themselves will contact each other before that happens. The bump stop is there to stop the spring movement just before the coils contact. Shorter spring, shorter bump stop to achieve that "stop just before contact".
 
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