R75/5 Front End Dive.

[Seth]

I don't have the specific specs on the spring, either the BMW ones or the Progressive.
But in general, the "tight" (softer) windings of the progressive springs are softer than stock and the "wide" winding are stiffer.
When you pull on the brakes and the front end dives, the "tight" windings on the Progressive springs compress easier than the "wide" windings until they coil-bind. Then the softer spring rate is eliminated and you're working with the wider stiffer spring rate.
The point of this is that your front end dive is probably more accentuated because of the Progressive springs. Stock springs, which are straight-rate, will initially compress less than the Progressive ones.

If you add more spacer to the Progressive springs, you will compress the softer tight windings more than the stiffer area. Therefore you'll have less dive before the stiff area of the spring kicks in. It will also lift the front end, reducing the "sag". Note what GSPD says above about "an inch or two" when you take your bike off the stand. Still, this might be what you are looking for.

It should also be noted that the dive of the front end changes the geometry, which increases feel and stability as you get on the brakes. From what you've written, that doesn't seem to be important. This geometry change does not occur much on the newer BMWs with the Telelever front suspensions, as they don't dive. Not great for racing, but very comfortable for normal road use. I notice you have an interesting collection of bikes, mostly older, but you may be interested in riding a newer BMW. Considering the "standard" setup of your /5, you may want to try an R1100R, R1150R, or R1200R with the Telelever suspension plus the Paralever rear which eliminates the rear end jacking under acceleration. They have a nice compliant ride without dive. I find the riding position to be a bit tighter than the older bikes, though.

You might find this site interesting...
http://cycle-ergo.com/
You can compare your bike (the only /5 they show is an R60/5) to the newer Oil and Hexhead models. You can adjust your height and inseam to see they affect the angles of your body.

[Tom H Ca]

Well I have some things to think about.

I do want to elaborate a bit more on the feel. We have the dive covered. The stiffness. Going over a long spaced washboard asphalt road like big rigs leave, the front almost feels like a rigid, as in no give. But then I go to stop and just touching the brake gives a dive.

I think I just may have to get over the dive and try to fix the rigid feeling. I think I will start off by pulling the original spacer and making a shorter set keeping the oil amount I have in it and see where it goes. Adjusting and trying. If that fails, maybe buy a new set of stock fixed rate springs.

Again, I was hoping it was a bad valve or the like that someone has already experienced.

Thank you all again so far!!!
Tom

[ME 109]

Sounds like stiction.
All bets are off if the front end is not aligned and binding.
Stiction is the lack of response to fine sharp road irregularities.
Stiction can be measured. Pump the suspension manly up and down and let the bars go on the up. Measure handle bars to ground.
Pump the suspension again and let it go on the down. Measure the bars to ground. The measurements should be almost the same.
If there is a significant discrepancy the fork are binding.

'Course I could be wrong. If I had a dollar for every time I was wrong with my RS, I'd have a pitiful contribution towards what being wrong has co$t me.

[Tom H Ca]

Stiction...hmmmm

When the front dives under braking, it comes right back up, smoothly/same as my other bikes come up. I never feel like the front end is staying down. I had a set of air shock on a bike that when I went over a certain RR track, the shocks would stay down for about 50 feet and then rise up. Strangest feeling. I will check this though to see if it is sticking a bit. Maybe I'm not noticing it on the road?

When I pull in to a driveway, I feel it compress and smoothly release. Sharper bumps seem to make the front end work better then rolling/long spaced washboard type bumps.

Thanks again!
Tom

[SteveD]

Hmmm - while you are in the forks why not consider the RT springs - together with the San Jose anti-dive springs under the damper rod in place of the buffer? Handling will now be a revelation compared to stock - still supple but with much reduced dive - trust me on this one .....and even better if you fit the San Jose fork brace...

This may not apply to the /5...dunno...but I read it today.

Any comments anyone?