Need Help Lightweight

[Davidlus]

Hi, Name‘s David. Been riding BMWs for a long time. Now an NC750x DCT. Arthritic fingers you see. Great bike, love it but as I’m only 130 lbs soaking wet I need to soften the suspension a bit, it’s wearing my false teeth away. Can I remove some oil from the forks?

 

[dduelin]

Hello David. For about $200 (last time I checked) a set of cartridge emulators from Cogent Dynamics will transform the forks and I think will give a better outcome than lowering the oil level. I weigh 145 and was able to use the stock springs.

 

[oldwisedude]

Did the Cogent fork upgrade alter the ride height? I would not expect it to do so but am interested to confirm.
My weight is 140lbs (probably 160 full rider weight) and 29" inside leg. My 2023 is already lower than your 2013 and I don't want to raise it.
I did write to Cogent some time ago but got no reply. Maybe they don't/can't export to UK.
Race Tech do a Gold Valve kit but spring values might be an issue.
The stock "one-size-fits-all" is decent for a 'cheapy', but the high-speed damping is crude and gets harsh, as we know.

 

[dduelin]

The Cogent DDCs are about 5/8” thick and set on top of the springs will increase ride height by that much. There is sufficient fender clearance to slip the fork legs up in the triple clamp to account for this so fork ride height doesn’t change.

 

[DirtFlier]

...or you can reduce the length of the spring spacer by 1/2-5/8" to retain the same ride height.

 

[potter0o]

I replaced the rear shock when it wore our and found that it helped improve the front end diving. YMMV

 

[Davidlus]

Thanks for your input. I did a bunch of research on fork springs, cartridges, oil levels, preload adjusting and all. Then I discovered a tire pressure genius, I mean a professional on the subject. To cut a long story short, I reduced the recommended front and rear tire pressures by 4lbs. And turned the rear preload down as far as it would go . Today I did a fast 200 mile run on mostly good pavement and my troubles are over. It’s a different bike now and I am really happy that the suspension does not need any further attention. Cost - zero

 

[the Ferret]

So you set your pressues at 32f and 38 r? 32 is awfully low for the front.

 

[Davidlus]

I agree, but it works. I checked and there was no heating at all. My riding style is not at all aggressive however on some freeway entrances and off ramps the bike felt very planted and stable when layed over and on the gas; very different to when the tyres were at “recommended pressures. I recommend that you research recommended tire pressures and find out why they are what they are. I also felt, for the first time, very safe at way higher than the legal speed limit with a strong cross wind.

 

[oldwisedude]

I agree, but it works. I checked and there was no heating at all. My riding style is not at all aggressive however on some freeway entrances and off ramps the bike felt very planted and stable when layed over and on the gas; very different to when the tyres were at “recommended pressures. I recommend that you research recommended tire pressures and find out why they are what they are. I also felt, for the first time, very safe at way higher than the legal speed limit with a strong cross wind.

Hi David. Thanks for an interesting discussion.

A bit more info please:-
1. I note that your weight is 130lb. What is your rider weight?
2. What make/model tyres are you running? (some makes like Bridgestone and Michelin seem to have stiffer sidewalls than others, such as Continental)

Manufacturer's recommended cold tyre pressures for motorbikes has always irritated me. For instance, if we were car drivers then we'd be advised to change the tyre pressures depending if we are two up, or five persons plus luggage, or sustained high speed driving etc. No such advice for motorcyclists. Whatever our modus operandi (with a few exceptions) our tyre pressures are listed as 36psi front, 42psi rear. So lightweights like you and I are told to use the same pressures as a 200 lb rider carrying a 160 lb pillion plus luggage! Ugh?

Is it that manufacturers don't think we bikers are intelligent or diligent enough to adjust pressures accordingly? Or is the one-size-fits-all approach merely a way of getting a reasonably, but not optimised, tyre pressure range that works most of the time for most of the users, keeping us reasonably safe and avoiding litigation?

I have written and spoken with tyre makers in the past but they cannot or will not explain the criterion. Only Continental came close to hinting that pressures might need changing for different conditions but did not commit or elaborate.

We lightweights cannot possibly be pressing the tyres into the tarmac by the same degree as a heavily-laden bike. The grip for us can feel skippy and harsh, as if its bouncing over irregularities rather than biting and gripping them. So your lower pressures must be counteracting this to an extent. Provided your hot running pressures do not rise more than 10% more than the cold pressures, then you'll probably be fine.

If we were to embark on a track day for example, you would not even be allowed down the pit lane until you had lowered the tyre pressures, in anticipation of the pressures increasing back nearer to optimal due to heat expansion when ridden in anger, in accordance with Boyle's Law.

In our "lightweight" situation the lower pressures will help with comfort. You are clearly achieving a more compliant contact patch which is conforming to the road, improving grip and confidence. If the handling is still predictable and to your liking then it is working for you and is a welcome free fix. It will have no effect on high speed compression or rebound damping - only the forks and shock can sort that out. But maybe on your roads you don't need anything more. In the UK we have some atrocious road surfaces that often break up mid-corner into choppy, rutted, destabilising sections. Thats where suspension upgrades pay back, but at a price.

 

[davidc83]

You are overthinking it. The recommended pressures on the tires and listed on the bikes swingarm are for max pressure carrying max weight. It is even listed as so in one of my manuals (if I can find it after my move). I don't go by that either, I run 40psi in all my tires on my 3 motorcycles and Prius C car. True adventure riders when they go off road on single track or sand track, reduce their air pressures to about 10 psi with no ill effects-they then increase the pressure once on asphalt. They will ride hundreds of miles down here in the dirt/sand with only 10 psi.

 

[Davidlus]

Hi Oldwisedude.
with me gear on I would guess about 140lb.
I have no idea what make the tires are and am too lazy to go down and take the cover off and look.
I‘m 86 now and built for comfort rather than speed. I don’t commute and only go out Saturdays, mostly urban traffic with the occasional long run to blow away the cobwebs. The wife comes along if it’s really a short ride!
living in Florida there’s very few twisties and no mountains- rather boring in fact. Our winters are great, 5C is beyond cold, now is perfect at about 25C and from now on it’s gets too bloody warm unless you get back home before 10am.
Here is a link that you might enjo:

Best, david

 

[dduelin]

Setting the correct psi for your riding weight can help ride comfort and enhanced rider feedback from the tires but does nothing for the suspension problems rooted in low budget components. I am glad you are happy with your suspension now.

 

[oldwisedude]

Hi Oldwisedude.
with me gear on I would guess about 140lb.
I have no idea what make the tires are and am too lazy to go down and take the cover off and look.
I‘m 86 now and built for comfort rather than speed. I don’t commute and only go out Saturdays, mostly urban traffic with the occasional long run to blow away the cobwebs. The wife comes along if it’s really a short ride!
living in Florida there’s very few twisties and no mountains- rather boring in fact. Our winters are great, 5C is beyond cold, now is perfect at about 25C and from now on it’s gets too bloody warm unless you get back home before 10am.
Here is a link that you might enjo:

Best, david

David. I admire and congratulate you for still bimbling out on your motorbike at 86! Well done, boy! I'm a mere 77 . As we suspected our road surfaces and climates are very different. Stay young in your mind. Best wishes.

 

[oldwisedude]

You are overthinking it. The recommended pressures on the tires and listed on the bikes swingarm are for max pressure carrying max weight. It is even listed as so in one of my manuals (if I can find it after my move). I don't go by that either, I run 40psi in all my tires on my 3 motorcycles and Prius C car. True adventure riders when they go off road on single track or sand track, reduce their air pressures to about 10 psi with no ill effects-they then increase the pressure once on asphalt. They will ride hundreds of miles down here in the dirt/sand with only 10 psi.

Hmm. I have had no such information on any of the swing-arms or manuals of any bike I have owned. Unlike the cars, which have detailed options for load and speed etc.

I cannot follow the logic in your running 40 psi all round in your bikes and car tyres without more explanation. For instance, I have owned cars that needed 24 psi F & R. If you increased much above that you merely wore the centre of the treads out faster and gained nothing in stability or grip.

Quote : "You are overthinking this". Really? Maybe you should tell that to Dave Moss? Although for the life of me I cannot see the logic in his premise either. He starts with Pirelli tyres that carry the usual 36/42 balance difference but then decides, without any explanation, to begin testing with 40/40.

As Spock would say ... " Fascinating"

 

[davidc83]

My car tires can go up to 50 psi per manufacturer. I run 40 because I get better mpg than 32psi and I get 75,000 miles on them at 40....just replaced them. On the bikes, I like the feel of 40 on both.

 

[oldwisedude]

That’s fair enough. It obviously works for you.
Interestingly, in the UK if you were unluckily enough to be involved in a road traffic accident, the Police would check your tyre pressures, amongst other safety items. If your pressures deviated significantly from manufacturer’s spec, then you could be prosecuted and/or your insurance revoked. Sobering thought.