Hello
Does any one Know what spring weight (400-600lb) the rear stock shock is ? When I get round to changing the Proflex one fitted I would Like some idea.I think I'm about 50 stone too light for the current one (not kidding).
Have a nice Xmass all
Rear Spring
Re: Rear Spring
Cant find the bit of paper that I wrote the standard spring rate down on, but I can tell you that I am about 13st in riding gear, and Roger at revolution racing reccomended an 825lb/in spring for me, and that is good.
I had previously used a 165N/mm 942lb/in spring, and although that was softer than the stock one, it was still too stiff [ohh err!].
If in doubt ring Roger at Revolution Uk, he will tell you what will work for you.........even if you dont buy anything off him, he is a font of all set up knowledge on the Firestorm and a really good bloke.
I had previously used a 165N/mm 942lb/in spring, and although that was softer than the stock one, it was still too stiff [ohh err!].
If in doubt ring Roger at Revolution Uk, he will tell you what will work for you.........even if you dont buy anything off him, he is a font of all set up knowledge on the Firestorm and a really good bloke.
AMcQ
-
Styler4077
- Posts: 344
- Joined: Thu Aug 31, 2006 9:50 pm
- Location: Bedford
Re: Rear Spring
13 Stone my butt......
My butt is 13 stone and all in all with the gear on weight close to 19 plus stone..
The shock compression spring is set as low as possible and the screw valve half way in, other wise is way to hard with lard butt on it.
mate ran round on his for two years with it fully screwed in and full compression...... He could hardly touch the ground, hated riding the bike over 30 miles as it gave him back ache....
My butt is 13 stone and all in all with the gear on weight close to 19 plus stone..
The shock compression spring is set as low as possible and the screw valve half way in, other wise is way to hard with lard butt on it.
mate ran round on his for two years with it fully screwed in and full compression...... He could hardly touch the ground, hated riding the bike over 30 miles as it gave him back ache....
"Only one life, so live it and ride a motorcycle"
-
revhead1957
- Posts: 2
- Joined: Thu Oct 07, 2010 10:16 pm
-
oldbikeman
- Posts: 280
- Joined: Sun Jul 25, 2010 3:32 pm
Re: Rear Spring
Wouldn't argue with anything Roger says on this subject.
Thanks
Thanks
Re: Rear Spring
I have been buliding up an excel spreadsheet for my 'storm, to calculate the optimum spring constants for the front forks and rear shock.
The spreadsheet includes bike and rider mass, with the front and rear mass distribution that I measured myself. Both front and rear unsprung mass has been estimated as well as the rear shock link ratio as I have not measured these.
Front unsprung mass estmated as 17 kg and rear unsprung mass estimated at 24 kg. Link ratio for the rear shock used is 1.8, dunno if that is correct.
From this I get and ideal rear shock spring constant as 68 N/mm. This is considerably lower than the values quotes here as converted to lb/in, this equates to 386 lb/in.
Maybe I have made a mistake or my approximations are too far out.
Other considerations are ride frequency, which was chosen as 1.8 Hz for road use.
Front spring constants come out at 8.5 N/mm (47 lb/in) for each fork, which seems right to me. This is of course for a linear spring not a progressive one.
The spreadsheet includes bike and rider mass, with the front and rear mass distribution that I measured myself. Both front and rear unsprung mass has been estimated as well as the rear shock link ratio as I have not measured these.
Front unsprung mass estmated as 17 kg and rear unsprung mass estimated at 24 kg. Link ratio for the rear shock used is 1.8, dunno if that is correct.
From this I get and ideal rear shock spring constant as 68 N/mm. This is considerably lower than the values quotes here as converted to lb/in, this equates to 386 lb/in.
Maybe I have made a mistake or my approximations are too far out.
Other considerations are ride frequency, which was chosen as 1.8 Hz for road use.
Front spring constants come out at 8.5 N/mm (47 lb/in) for each fork, which seems right to me. This is of course for a linear spring not a progressive one.
Re: Rear Spring
Fozzy, I think there must be a bit of a mix up in your calculations, that sounds much too low a rate, more than 50% lower than stock...................Your belly pan will be dragging on the floor when you get on the bike with that I think...............Did you foget to add the rider weight?
AMcQ
-
oldbikeman
- Posts: 280
- Joined: Sun Jul 25, 2010 3:32 pm
Re: Rear Spring
Some shock suppliers (Proflex,Race-tech,Honda) are saying over 900lbs but I know this is too hard even for racing .
Re: Rear Spring
They may well be allowing for the possible additional weight of a pillion and luggage (max laden weight). Manufacturers have to fit a spring to cover the maximum possible weight, for health and safety reasons, as they could be sued otherwise as it's a "reasonably foreseeable" load, and the vehicle has to be able to safely cope with it.
However, if you're not taking a pillion, don't load it for two weeks' touring etc, then a lower spring rate will be all that you need.
I suspect that the higher rates are more to cover themselves than anything else, but why take up valuable adjustment range with settings you'll never use?
However, if you're not taking a pillion, don't load it for two weeks' touring etc, then a lower spring rate will be all that you need.
I suspect that the higher rates are more to cover themselves than anything else, but why take up valuable adjustment range with settings you'll never use?
It's not falling off, it's an upgrade opportunity.
Re: Rear Spring
The calculations are based purely on my mass (12 stone) and with no provisions for luggage etc... as I ride mainly solo. I have also made a few assumptions although I think they are fair ones.
These provisions for the manufacturer covering themselves is of course a very good point. For road use and always riding alone, for me personally, it could possibly be a fairly good set up as the bike mass was measured with me front and rear with very light support so as to not affect the load distribution of actual mass values.
Interesting to have real values and compare them to my model as it can be hard to validate sometimes, wish I had the budget to get a load of springs and try them out to make some comparisons, but don't
These provisions for the manufacturer covering themselves is of course a very good point. For road use and always riding alone, for me personally, it could possibly be a fairly good set up as the bike mass was measured with me front and rear with very light support so as to not affect the load distribution of actual mass values.
Interesting to have real values and compare them to my model as it can be hard to validate sometimes, wish I had the budget to get a load of springs and try them out to make some comparisons, but don't
Re: Rear Spring
If you take advantage of suspension set-up offers at some retailers, you will probably be able to try different springs- they'll let you have a go on the ones they suggest, but if you ask to try a different one they can just put a different spring on for you to try.
They'll probably be right first time, though!
My only concern with fitting a lighter spring and planning no pillion/luggage is if you sell the bike- maybe a note staple to the logbook/V5 to remind you to tell the next owner? And if you change the whole shock keeping the old one to include in the sale might be a good idea as well.
They'll probably be right first time, though!
My only concern with fitting a lighter spring and planning no pillion/luggage is if you sell the bike- maybe a note staple to the logbook/V5 to remind you to tell the next owner? And if you change the whole shock keeping the old one to include in the sale might be a good idea as well.
It's not falling off, it's an upgrade opportunity.
Re: Rear Spring
Yeah, that may well work. If the bike was set up for me then it would never be sold without being put back to standard or some serious explanation on the mods.
Not that I am planning on getting rid of the 'storm
as it is a fantastic, underrated machine. Bit thirsty but what a great motor, just the suspension that lets it down really.
Thanks guys, when I can afford it I will be upgrading but until then she will be bouncing around at the back and scuba diving at the front!!!
Not that I am planning on getting rid of the 'storm
as it is a fantastic, underrated machine. Bit thirsty but what a great motor, just the suspension that lets it down really. Thanks guys, when I can afford it I will be upgrading but until then she will be bouncing around at the back and scuba diving at the front!!!
Re: Rear Spring
Fozzy,
I have now found the bit of paper where I noted down some info following my talk with Roger Dichfield.
standard Honda spring is 950lb/in [or 170kg/mm]
Linkage ratio 2:1
His comments for a 13st [in riding gear] fast solo road use with a few track days-------no higher than 800lb/in [14.25kg].
Tony is also correct when he makes a warning on the potential impact when taking a pillion with moded suspension. On my bike with the 800 spring set for 1 up [8mm sag and 5mm extra ride hieght] just adding a 9 stone pillion screwed up the handleing and had the belly pan grounding out on bumps mid corner.
Yes..............changing the preload should be one of the solutions, but with a race shock that can be more than 40mins task with c-spanners and hammers, so you need to take into account that by optomising solo performance you compromise all other areas.
That was the reason I sold my WP shock and replaced it with a Nitron shock........I used the same 800lb spring rate, but bought a shock with a remote preload adjuster, so I could still take a pillion when I wanted, and then revert quickly back to the solo settings.
Would reccomend to anyone swapping shocks to keep the standard one for when you sell the bike, then sell the good shock on e-bay........you will get more of your money back this way, and also the bike will be sold without compromise on the fully loaded performance.
I have now found the bit of paper where I noted down some info following my talk with Roger Dichfield.
standard Honda spring is 950lb/in [or 170kg/mm]
Linkage ratio 2:1
His comments for a 13st [in riding gear] fast solo road use with a few track days-------no higher than 800lb/in [14.25kg].
Tony is also correct when he makes a warning on the potential impact when taking a pillion with moded suspension. On my bike with the 800 spring set for 1 up [8mm sag and 5mm extra ride hieght] just adding a 9 stone pillion screwed up the handleing and had the belly pan grounding out on bumps mid corner.
Yes..............changing the preload should be one of the solutions, but with a race shock that can be more than 40mins task with c-spanners and hammers, so you need to take into account that by optomising solo performance you compromise all other areas.
That was the reason I sold my WP shock and replaced it with a Nitron shock........I used the same 800lb spring rate, but bought a shock with a remote preload adjuster, so I could still take a pillion when I wanted, and then revert quickly back to the solo settings.
Would reccomend to anyone swapping shocks to keep the standard one for when you sell the bike, then sell the good shock on e-bay........you will get more of your money back this way, and also the bike will be sold without compromise on the fully loaded performance.
AMcQ
Re: Rear Spring
AMCQ,
Thanks for the information mate. Using the correct link ratio has provided better results (480 lb/in , 83.5 N/mm). I now believe choosing a suitable ride frequency will provide the correct set up for solo riding and using the correct, instead of estimated unsprung masses.
I think my model has some degree of suitability although not perfect and not suitable for compromise with carrying others/luggage etc. Of course the masses can be changed but the masses used are suitable to me personally at the moment sat on the bike.
Cheers Fozzy
Thanks for the information mate. Using the correct link ratio has provided better results (480 lb/in , 83.5 N/mm). I now believe choosing a suitable ride frequency will provide the correct set up for solo riding and using the correct, instead of estimated unsprung masses.
I think my model has some degree of suitability although not perfect and not suitable for compromise with carrying others/luggage etc. Of course the masses can be changed but the masses used are suitable to me personally at the moment sat on the bike.
Cheers Fozzy