Lowering circle of frustration

[Mudchute]

I'm one of the vertically challenged (30"inseam) and so went down the OEM lowering links and low seat rout with my T7, plus an 80 nm spring and a 10mm fork drop. This should have lowered the ride height by 38mm from stock.

 

With this setup, I still found I could only just get the balls of my toes on the ground, which is weird IMHO because I weigh 100kg  - 2220 lb in kit and have crash bars, skid plate, side case and top case racks fitted. Setting the rider sag was also a bit strange in that I needed to pile on a lot of preload to get to the recommended 60mm.

 

OK I thought and fitted the RRP 40mm bones and, remembering that this would even further reduce the effective spring rate, fitted the 95 nm RRP spring to compensate and dropped the forks by the recommended 20mm. Now here's the rub. I had expected that with the 40mm bones, 20mm fork drop and 95 nm spring, I'd only have to wind on minum preload to get the correct rider sag, but no.. In order to get the right sag I'm STILL winding on 18 clicks from no preload which raises the ride height by almost 10 mm and I'm back where I started, nearly on tiptoes, (I know some folks can cope with this, I'm not one of them)

 

Clearly I've gone the wrong way somewhere - anyone been down this route that could offer any pointers? All advice gratefully received 

 

 

[Yamablueridge]

Mud, that’s a bummer. I remember seeing something about a .5nm drop in spring rate with a 20mm bone. I’m no suspension expert but it would seem that the 40mm is dropping the 95nm to <8.5.
 

And I’d think the drop in spring rate is not linear across the bone length, the 40mm should be >than 1nm.

 

It sucks that your collecting springs, but on the bright side you must be getting good at removing and installing the springs. 

 

Maybe a super stiff 105 would get you in the ballpark, not sure where you’d find one Ktech?
 

I’m a little dude 77kg, 80kg in gear so at the moment the stock springs are going to be at the tail end of my modifications. 
 

[BLZ2DWL]

Hmm. When you install lowering links, you are shifting the overall travel of the rear wheel upwards toward the tail; essentially raising the rear wheel in the stroke. Therefore the fully extended measurement is shorter, meaning your static sag and rider sag will also be shorter(same MM as before, i.e 20mm/60mm). Therefore it seems impossible for the ride height to be the same as before you lowered it if you have the same rider sag in both scenarios. 

 

Can you walk us through your process for setting the sag?

Edited November 6, 2022 by BLZ2DWL
Correction

[Uncle M]

@Mudchute Contact Rally Raid for recommendations?

[Mudchute]

Hi Uncle M - RRP recommend adding to the rider weight if you have the 40mm RRP lowering bones by 15%. Then you can select the correct RRP spring. This is their calculation which takes into account the loss of spring rate due to the longer bones. So I'm pretty much by the book I think as far as the recommended RRP settings are concerned.

 

"NOTE: If fitting lowering links, add 10% to rider weights for 20mm link, and 15% for 40mm links, to compensate for changes in rising-rate geometry."

[Mudchute]

Hi BLZ2DWL

 

Yep, it's a puzzle. I measure the static and rider sag in the usual way  - marked point on bike perpendicular the the rear axle and I measure  the distance between the two with the wheel unloaded for static sag, with the bike on its wheels and then with me on the bike in gear plus a nominal amount of luggage for rider sag. I'm looking for 10% of the stock travel for static and 30% for rider sag with a tolerance of 10mm either way.

 

I think what you're saying is that if you reduce the travel by 40mm, so 160 instead of 200mm, that should be my starting point  - so instead of 30% of 200mm = 60mm rider sag with the stock bones, I should be looking for 30% of 160mm for rider sag e.g. 48mm?

 

That kinda makes sense, though RRP doesn't make that point anywhere that I can see, whereas with their spring rates, they definitely take lowered bones into account  

 

 

[Mudchute]

On 10/29/2022 at 10:23 AM, Yamablueridge said:

Mud, that’s a bummer. I remember seeing something about a .5nm drop in spring rate with a 20mm bone. I’m no suspension expert but it would seem that the 40mm is dropping the 95nm to <8.5.
 

And I’d think the drop in spring rate is not linear across the bone length, the 40mm should be >than 1nm.

 

It sucks that your collecting springs, but on the bright side you must be getting good at removing and installing the springs. 

 

Maybe a super stiff 105 would get you in the ballpark, not sure where you’d find one Ktech?
 

I’m a little dude 77kg, 80kg in gear so at the moment the stock springs are going to be at the tail end of my modifications. 
 

Thanks Yamablueridge - some interesting comments here - I think DLZ2DWL may well have solved the mystery for me  - looks like that answer might have been hiding in plain sight :-)

[Mudchute]

1 hour ago, Mudchute said:

Hi Uncle M - RRP recommend adding to the rider weight if you have the 40mm RRP lowering bones by 15%. Then you can select the correct RRP spring. This is their calculation which takes into account the loss of spring rate due to the longer bones. So I'm pretty much by the book I think as far as the recommended RRP settings are concerned.

 

"NOTE: If fitting lowering links, add 10% to rider weights for 20mm link, and 15% for 40mm links, to compensate for changes in rising-rate geometry."

Though checking BLZ2DWL's post it may be the reduced travel at the bottom of it - have emailed RRP with that question 

[Fredlock]

I think you’re worried about sag too much. Set the ride height where you can touch and feel comfortable. Then ride it. Sag is a suggestion not a rule. People take luggage on and off their bike all the time they don’t reset the sag every time. Just be comfortable touch the ground and go ride. Just my opinion 

[Mudchute]

16 hours ago, Fredlock said:

I think you’re worried about sag too much. Set the ride height where you can touch and feel comfortable. Then ride it. Sag is a suggestion not a rule. People take luggage on and off their bike all the time they don’t reset the sag every time. Just be comfortable touch the ground and go ride. Just my opinion 

I get what you're saying Fredlock, but I would like to get the suspension working at least somewhere within the correct range. At the moment, the front end is understeering and the rear end harsh. Setting the correct sag is the first step to a good setup but as you say, in no way mandatory. 

Edited October 31, 2022 by Mudchute

[Mudchute]

On 10/29/2022 at 2:46 PM, BLZ2DWL said:

Hmm. When you install lowering links, you are reducing the overall travel of the rear wheel; essentially raising the rear wheel in the stroke. Therefore the fully extended measurement is smaller, meaning your static sag and rider sag will also be smaller (same percentage of full extension, i.e. 30% rider sag, but full extension is smaller MM). Therefore it seems impossible for the ride height to be the same as before you lowered it if you have the same % rider sag in both scenarios. 

 

Can you walk us through your process for setting the sag?

Hi BLZ2DWL

 

Yep, it's a puzzle. I measure the static and rider sag in the usual way  - marked point on bike perpendicular the the rear axle and I measure  the distance between the two with the wheel unloaded for static sag, with the bike on its wheels and then with me on the bike in gear plus a nominal amount of luggage for rider sag. I'm looking for 10% of the stock travel for static and 30% for rider sag with a tolerance of 10mm either way.

 

I think what you're saying is that if you reduce the travel by 40mm, so 160 instead of 200mm, that should be my starting point  - so instead of 30% of 200mm = 60mm rider sag with the stock bones, I should be looking for 30% of 160mm for rider sag e.g. 48mm?

 

That kinda makes sense, though RRP doesn't make that point anywhere that I can see, whereas with their spring rates, they definitely take lowered bones into account. Update, I still haven't received a reply from RRP, however it would seem from what I've read elsewhere, that fitting the lowering bones does not alter the rear wheel travel, it's still 200mm but the whole shooting match has now moved nearer to the underside of the bike, hence the warning on the RRP site about "extreme use". I guess whoops and jumps could be quite interesting with the 40mm kit on, fortunately I have a CRF 250 for that 

 

[BLZ2DWL]

I see what you mean. Let me restate to be more precise. Overall wheel travel is the same, yet you have now moved the range of travel closer to the bike. If thinking about the rear wheel axles, both the fully extended and fully compressed points are now closer to the tail. That is why RR warns that you could now compress the rear wheel into the undertail. However, you fitted a stiffer spring and hopefully can prevent bottoming out. Now when you measure full extension, the distance between the rear axle and a fixed point above it (lets call that dimension A) is 40mm less than before you installed the lowering links and new spring. So if you want 30% rider sag (let's call that dimension B) of 200mm travel, you adjust until B=A-60mm. Assuming you did the same thing before installing the lowerling links, your new measurement of B cannot be the same. Yet you seem to be saying that B is the same before and after the link install.  

 

Example:

• Before lowering links: 
  • A = 250MM
  • Rider sag 30% of 200 = 60MM
  • B = 190MM
• After lowering links:
  • A=210MM
  • Rider sag 30% of 200 = 60MM
  • B=150MM

 

[Yamablueridge]

BLZ, that kinda matches my train of thoughts (still not 100% sure). The rear travel will not decrease, I would imagine the rear shock is the limitation with the travel. The link will not remove 20-40mm of travel from the shock, it lowers the mounting point. The initial unloaded wheel measurement will be 20-40 mm less and the travel remains the same, so the sag specs remain unchanged but we need to start with the lower initial measurement. 
 

Does that sound right? 
 

I always begin the day with a question mark….

[Mudchute]

Hey - for the reply. I see what you're say but no, I'm still using 60mm as 30% of the total travel because as you say, that doesn't change, the range, it just gets closer to the undertray. What I'm saying is that I'm not getting the seat height reduction  I'd expect after fitting a low seat and the RRP 40mm links and compensating for the reduction in spring rate caused by the lowering links and correctly setting the rider sag.

 

In order to get the rider sag within the 60mm range (RRP state +-10mm) I have to wind on about 90% of available preload, which raises the ride height by about 9mm, something I thought would not happen, having fitted the stiffest RRP spring.

 

 

 

 

[AirborneSilva]

Some good information here, I calculated my rider sag at 21% but I'm thinking I calculated wrong (math was never my strong suit).  I'm a "short" rider with 29" inseam and present weight is 157 lbs.  I'll have to try and re-calculate after studying some of the responses to see if it makes sense to my non-mathamatical mind...