Steaksauce
New Member
So I'm redoing a 72 SL125 for a bike to cruise around town on. My question is will the forks be ok for the street or should I look In to CB forks or even the whole front end?
Question on forks
- Thread starter Steaksauce
- Start date
nrcb125
Been Around the Block
They'll probably be fine on the road. Ride the bike as is for a bit and then make adjustments. If you want to replace the wheel to get a disc brake up front that's another story...
Rather than replacing the front end you could try stiffening the springs a little and changing to a slightly thicker fork oil.
To stiffen the springs cut a little bit off usinga band saw a miter box/saw (thanks xb33bsa!) for a clean cut and add in a spacer to make up for the length removed. There's a bunch of calculators on the internet to help you figure out the new rate. This will make the front end stiffer.
Here's a good guide to cutting the stock springs:
http://www.ex-500.com/wiki/index.php?title=Upgrading_the_Suspension#Cutting_Stock_Springs_.28_The_FOG_suspension_Mod_.29
Replacing with a heavier weight fork oil will slow the damping in the front forks. Find the recommended fork oil weight in a shop manual and go up one rating. For example if it says 10W, try 15W.
The best part is doing both of these is really inexpensive
Rather than replacing the front end you could try stiffening the springs a little and changing to a slightly thicker fork oil.
To stiffen the springs cut a little bit off using
Here's a good guide to cutting the stock springs:
http://www.ex-500.com/wiki/index.php?title=Upgrading_the_Suspension#Cutting_Stock_Springs_.28_The_FOG_suspension_Mod_.29
Replacing with a heavier weight fork oil will slow the damping in the front forks. Find the recommended fork oil weight in a shop manual and go up one rating. For example if it says 10W, try 15W.
The best part is doing both of these is really inexpensive
a bandsaw ? no, you will ruin every blade :nrcb125 said:They'll probably be fine on the road. Ride the bike as is for a bit and then make adjustments. If you want to replace the wheel to get a disc brake up front that's another story...
Rather than replacing the front end you could try stiffening the springs a little and changing to a slightly thicker fork oil.
To stiffen the springs cut a little bit off using a band saw for a clean cut and add in a spacer to make up for the length removed. There's a bunch of calculators on the internet to help you figure out the new rate. This will make the front end stiffer.
Here's a good guide to cutting the stock springs:
http://www.ex-500.com/wiki/index.php?title=Upgrading_the_Suspension#Cutting_Stock_Springs_.28_The_FOG_suspension_Mod_.29
Replacing with a heavier weight fork oil will slow the damping in the front forks. Find the recommended fork oil weight in a shop manual and go up one rating. For example if it says 10W, try 15W.
The best part is doing both of these is really inexpensive
you will need an abrasive disc to cut a springgood info otherwsie
yes that is true if you heat it in the middle and a large portion of the coils that is what the mexicans used to do to get a lowriderSav0r said:
i was talking about the very end it works perfectly as i outlined without any issues
and it is the only correct way to shorten a spring, as you must close the end of a spring by heating it and bending it down and then grinding it flat so it stands straight
we are only talking about heating the last half coil
Just out of curiosity why not just jam in a spacer and leave the spring length? Why does shortening the spring cause it to be stiffer?
I figured you'd want to increase the preload like the adjusters on some rear shocks by just dropping a stack of quartets on top of the springs.
I figured you'd want to increase the preload like the adjusters on some rear shocks by just dropping a stack of quartets on top of the springs.
+1. Cutting springs increases stiffness??? I don't think so. Lowers the ride height, usually not a good idea on an older bike without considering everything else. Spacers will increase the preload making the bike feel stiffer, and likely increasing rider confidence, so that and experimenting with the fork oil sounds good. Most riders find stiffer suspension an improvement if they have crap damping. This results in always wanting very stiff suspension because it feels more sure footed. Really good damping allows much softer support and the tires stay better planted over bumps in turns. But you have to have the damping. If you have crappy damping on older machinery like I do, stiffer is the only affordable way.
yes shortening a spring increases its rate,the dif is made up with a spacer
and it is the best way to stiffen up the front
you can only go so far shortening a spring before coil bind is an issue
just adding preload is acceptable only to a point, when so much preload is added that a fork tends to top out too easy and static sag is not enough then it is a detriment
ideally the correct spring rate is used without over preloading the spring
there are spring calculators online that allow you to plug in the physical dimensions of any spring
gives you the spring rate voila
this way you can more easily/confidentilly ruin a spering ;D
and it is the best way to stiffen up the front
you can only go so far shortening a spring before coil bind is an issue
just adding preload is acceptable only to a point, when so much preload is added that a fork tends to top out too easy and static sag is not enough then it is a detriment
ideally the correct spring rate is used without over preloading the spring
there are spring calculators online that allow you to plug in the physical dimensions of any spring
gives you the spring rate voila
this way you can more easily/confidentilly ruin a spering ;D
sav0r
Coast to Coast
The shorter the torsion bar the stiffer the spring. Coil springs are nothing more than wound torsion bars.
Increasing preload adds a rate threshold that you have to overcome to make the suspension move. That means initially the suspension is stiff feeling, which might feel like an improvement, but once the suspension starts to move the spring works as it did before. This can result in a harsh ride over high speed bumps, but no improvement in overall rate. You want enough preload to support the bike properly but too much is a quickly losing battle because like others have mentioned it can have some nasty side effects.
Increasing preload adds a rate threshold that you have to overcome to make the suspension move. That means initially the suspension is stiff feeling, which might feel like an improvement, but once the suspension starts to move the spring works as it did before. This can result in a harsh ride over high speed bumps, but no improvement in overall rate. You want enough preload to support the bike properly but too much is a quickly losing battle because like others have mentioned it can have some nasty side effects.
