Suspension Upgrades

[Syscrush]

In both principle and practice, I agree completely with your mechanic - which is why I've gone the way I have (stock-length forks, near-stock wheel/tire sizes, stock-or-better ground clearance, small change to rake, medium change to trail, small change to bar position, drastically improved damping).

I haven't ridden any of the bikes with swapped-on USD (including triples from a different bike) and 17" wheels, and the owners of those bikes report that they're happy with them - but it's not a direction that I'd be comfortable going.

If I was starting from scratch now, I'd probably go with 43mm Ohlins RSU forks. The route I took looks more OEM, but has as much (or more) customization as going that route would require, and similar cost. With that said, someone who was OK with 2-piston brakes and upgraded pads & lines, and stock trail would do well to do the AK-20 in Pro-Link forks setup as it's bolt-on.

Also, I am extremely pleased with how the bike handles now. And I am a fussy mf'er who is not easily pleased.

Your mechanic's plan sounds good to me. Even a set of RTCE's will make a world of difference to that bike. If he can fit cartridge internals in the 37mm forks (which should be possible - I know of vintage BMW bikes with carts in their 35mm forks), that's even better.

[wyly]

In both principle and practice, I agree completely with your mechanic - which is why I've gone the way I have (stock-length forks, near-stock wheel/tire sizes, stock-or-better ground clearance, small change to rake, medium change to trail, small change to bar position, drastically improved damping).

I haven't ridden any of the bikes with swapped-on USD (including triples from a different bike) and 17" wheels, and the owners of those bikes report that they're happy with them - but it's not a direction that I'd be comfortable going.

If I was starting from scratch now, I'd probably go with 43mm Ohlins RSU forks. The route I took looks more OEM, but has as much (or more) customization as going that route would require, and similar cost. With that said, someone who was OK with 2-piston brakes and upgraded pads & lines, and stock trail would do well to do the AK-20 in Pro-Link forks setup as it's bolt-on.

Also, I am extremely pleased with how the bike handles now. And I am a fussy mf'er who is not easily pleased.

Your mechanic's plan sounds good to me. Even a set of RTCE's will make a world of difference to that bike. If he can fit cartridge internals in the 37mm forks (which should be possible - I know of vintage BMW bikes with carts in their 35mm forks), that's even better.

When I told him I was going let him do what he thought was best he seemed relieved I wasn't going attempt it on my own and get myself killed. His first choice was RTCE and springs but I'll mention the cartridge option. The RTCE install eliminates the anti-dive feature at the same time. He's already told me he'd like a larger front wheel at least 17" preferably 18", less twitchy than the oem 16" and a better tire selection.

He's pleased I'm improving a vintage bike he said while it might be a little heavy in comparison with new bikes with my carb and header improvements it'll be comparable to many and better than others in HP(estimated 140-145 at crank) and torque (90ft lbs). Add in improved braking and handling I should have a great vintage ride. I'll keep you apprised of how it progresses.

[Syscrush]

The RTCE install eliminates the anti-dive feature at the same time.

It also eliminates the need for it.

Braking forces are a low-speed input (we're talking about the speed of the motion compressing the fork here, not the road speed), while hitting a pothole is a high-speed input (as this jars the wheel and compresses the fork hard/fast). Damping rod forks offer very little resistance to low-speed inputs, and lots of resistance to high-speed inputs. So, a damping rod front end is mushy and dives when you're on the brakes, and stiff AF when you hammer a pothole at speed. Ideally, we want the exact opposite of that. RTCE's get us close, a proper full cartridge gets us closer, a full cartridge setup with separate compression & rebound adjustments gets us closer still, and a super-fancy full cart with separate high and low speed rebound & compression lets us really dial in the best compromise for any given conditions.

The anti-dive setups we saw in the 80's were a patch for damping rod forks. They use brake line pressure as a signal to increase damping. So they can run softer in normal use (and be less likely to buck you off when hitting a sharp bump) without the dive going out of control when braking (especially sustained, smooth braking). Just don't hit a bump when trail-braking.

With the RTCE's in place, you don't need the patch or workaround of the brake-linked anti-dive.

[wyly]

The RTCE install eliminates the anti-dive feature at the same time.

It also eliminates the need for it.

Braking forces are a low-speed input (we're talking about the speed of the motion compressing the fork here, not the road speed), while hitting a pothole is a high-speed input (as this jars the wheel and compresses the fork hard/fast). Damping rod forks offer very little resistance to low-speed inputs, and lots of resistance to high-speed inputs. So, a damping rod front end is mushy and dives when you're on the brakes, and stiff AF when you hammer a pothole at speed. Ideally, we want the exact opposite of that. RTCE's get us close, a proper full cartridge gets us closer, a full cartridge setup with separate compression & rebound adjustments gets us closer still, and a super-fancy full cart with separate high and low speed rebound & compression lets us really dial in the best compromise for any given conditions.

The anti-dive setups we saw in the 80's were a patch for damping rod forks. They use brake line pressure as a signal to increase damping. So they can run softer in normal use (and be less likely to buck you off when hitting a sharp bump) without the dive going out of control when braking (especially sustained, smooth braking). Just don't hit a bump when trail-braking.

With the RTCE's in place, you don't need the patch or workaround of the brake-linked anti-dive.

I was initially going to install a bolt on exterior plate that eliminates the anti-dive for $150 but the RTCE isn't much more money and does the same. It was a no brainer.

I've heard of fork set ups with compression in one fork leg and rebound in the other is this what you're referring to? And not both features in the same fork leg?

[Rick Pope]

<<I've heard of fork set ups with compression in one fork leg and rebound in the other is this what you're referring to? And not both features in the same fork leg?>>

I believe many modern bikes have this feature. My Moto Guzzi does.

[Syscrush]

I've heard of fork set ups with compression in one fork leg and rebound in the other is this what you're referring to? And not both features in the same fork leg?

What I'm referring to is having separate, external adjusters for compression and rebound. Entry-level cartridge forks (like on the low-spec Ducati Monsters) have either no adjustment, or rebound-only. The trend recently has been towards compression duties handled by one fork and rebound by the other - which goes hand-in-hand with the adoption of large diameter front axles (which basically does the work of a fork brace - making the two fork lowers move as a single unit) - but there are lots of OEM and aftermarket setups out there with both compression and rebound damping in each of the two forks.

I am sure that I've seen high-end forks with separate high & low speed damping settings, but I can't find any examples now. It's pretty common in shocks, though.

Another approach that's common in shocks but only in the high end of forks is gas charging.

Have you thought about a budget setup like this?

[EMS]

Have you thought about a budget setup like this?

Wow, Phil! I assume this is a tongue-in-cheek remark. Brembo radial calipers, Öhlins forks...some kind of budget that is

[Rick Pope]

Have you thought about a budget setup like this?

Wow, Phil! I assume this is a tongue-in-cheek remark. Brembo radial calipers, Öhlins forks...some kind of budget that is

Mike, it's easy to miss the little guy under the picture rolling and laughing. I admit, it took me a minute.....

[wyly]

Have you thought about a budget setup like this?

yeah, right... I could probably buy a stable full of GS1150's for the price of the front end setup. A brake conversion to Brembos would be nice

I've been searching for cartridge conversions for my oem forks without success unless my mechanic comes up with a conversion of his own design. I've no doubt given his talents and resources he could but at what cost At this point my best option still appears to be the RTCE. I sent him a text asking if K-tech has cartridge conversion that would work at a sensible price point.

:edit: 30 seconds after I send the text I get a response... " NO, RTCE is definitely the best option for any street bike" gotta love a mechanic who when given the option of spending more money looks after my best interest and budget.

[Syscrush]

Wow, Phil! I assume this is a tongue-in-cheek remark. Brembo radial calipers, Öhlins forks...some kind of budget that is

Carbon wheels, too. We're looking at a $12k set of forks, and I think at least $3k worth of calipers (assuming those are the GPRR monoblocs).

You know, your basic bolt-ons.

[wyly]

Wow, Phil! I assume this is a tongue-in-cheek remark. Brembo radial calipers, Öhlins forks...some kind of budget that is

Carbon wheels, too. We're looking at a $12k set of forks, and I think at least $3k worth of calipers (assuming those are the GPRR monoblocs).

You know, your basic bolt-ons.

is that all...and here I was thinking they were something I couldn't afford

[wyly]

They're off, it was a bit of a struggle.

Next week I take them in to be rebuilt and modified to be as good as they can be considering the size of my budget and they're 36 yrs old.

[wyly]

<<I've heard of fork set ups with compression in one fork leg and rebound in the other is this what you're referring to? And not both features in the same fork leg?>>

I believe many modern bikes have this feature. My Moto Guzzi does.

I asked my suspension guy about that and he said it was done that way primarily because it was less expensive than putting both features in each fork leg.

[wyly]

Wow, Phil! I assume this is a tongue-in-cheek remark. Brembo radial calipers, Öhlins forks...some kind of budget that is

Carbon wheels, too. We're looking at a $12k set of forks, and I think at least $3k worth of calipers (assuming those are the GPRR monoblocs).

You know, your basic bolt-ons.

I was checking out the Brembos on a track bike in my mechanics shop, he's said there are more basic entry level Brembo's(still expensive) but expect to pay $5K for the better Brembo calipers I was looking at.

I got my forks returned, completely rebuilt and polished, better than new . PDF and air assist both eliminated he asked me my riding style preference for set up but I let him set it up as he thought best. $550 materials $250 labour, I did it for less on my CBX but I didn't do all the work he did, I don't mind paying for expertise when my actual life depends on it. As the GS will be considerably quicker than the CBX and I feel better knowing it was done the best it can be for a 36yr old vintage rocket.

I also had him made new brake lines eliminating the 3 line splitter set up, I expected something simple and basic but he gave more $$$ compound fittings that can be adjusted for different caliper options. I forgot we had spoken a couple months back about going with different wheel sizes and calipers in the future and remembering that he built that feature into the fittings to prepare for the conversion. Yeah those $5K Brembos will fit no problem now

[bikeymikey748]

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