Front fork strength

Paul Heim SuprHtr at
Fri May 16 20:23:28 PDT 2008


I agree with Charles.  The cheapest approach to stiffen the front end is to 
add preload.  Washers are easy, and only slightly more effort is to cut some 
PVC pipe to length.  Stiffer springs are the third option, and I paid about 
$80 for a pair from Sonic Springs.  I got the data from the RaceTech 
website, but their springs were out of stock forever and I diverted to Sonic 
at Murph's suggestion.  As I've said before, and as Charles has confirmed, I 
went too stiff (1 kg/mm) but found that they work VERY well for riding 2-up. 
I almost always ride 2-up on the Geeper, so I'm guessing .85 kg/mm would be 
much better for solo riding.  Charles advocates stock springs with added 
preload, but I think I'll put my GPz stock springs in my ZR-7!  Unless the 
Progressive springs I bought 2 years ago for the ZR work out...  I really 
need to install those someday.

Paul in Ohio
----- Original Message ----- 
From: <blackbear at>
To: <gpzlist at>
Sent: Friday, May 16, 2008 10:01 AM
Subject: Front fork strength

> I installed a high-note car horn when the stock horn died on  the 
> GPZ.  I thought there was plenty of room between the fender and  the horn, 
> but I noticed the top of the (fairly newly painted) fender  has been worn 
> down to the plastic and the horn is damaged.
> I checked, and it feels like the forks are compressing a LOT more than  I 
> was used to.
> I had the oil changed a couple years ago when I had the seals  replaced. 
> using the mix of 10w and 15w that Scaps recommended.
> Is there any way of strengthening the front end short of cartridge 
> emulators?  i can't really afford that kind of conversion at this time.
> i will also look at ways of moving the horn so it won't hit anymore.   I 
> put it where the stock one was as I was in a hurry to get the bike 
> inspected.
> Michael in holley, NY

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