Survived a spring swap!

[Dave D]

K-Tech 90 N/mm linear spring arrived. No local bike shops have a shock compressor. Soooo:

 

 

 

 

Had to super glue the metal collar to the pivot block to get it to stay at the top.

 

 

Spring size comparison. 90 N/mm obviously fatter.

 

 

I survived! Yay.

 

The whole thing wanted to flip over towards the handle end of the jack but some careful holding and keeping well back did the job. I will modify this so there is a brace each side to keep it all square to the jack.

 

The bike feels much nicer with my fat ass on it now. I am 89 kg's without kit. Height wise it is still very manageable. I had to fit 20mm lowering links and drop the forks a tad to get it comfortable. Feels more like a motorcycle now and less like a motorised bowl of custard.

 

I am in North Devon, UK, if anyone wants to use it.

[Lewie]

Well done

im about 95kg and was toying with the idea of a RR replacement- don’t fancy the thought of doing it myself though 

[Endopotential]

Nicely done!  I'm a bit of a lightweight at only 155lb / 70kg bare, but I'm surprised how bouncy the stock spring is.  Though I did lower the bike about 30mm, and I read that changing that distance adds leverage to the system and functionally makes the spring feel softer.  Any truth to that?

I'm thinking I'll eventually swap to a 85 N/mm spring.  Does that sound right?

[Windblown]

3 hours ago, Endopotential said:

Nicely done!  I'm a bit of a lightweight at only 155lb / 70kg bare, but I'm surprised how bouncy the stock spring is.  Though I did lower the bike about 30mm, and I read that changing that distance adds leverage to the system and functionally makes the spring feel softer.  Any truth to that?

I'm thinking I'll eventually swap to a 85 N/mm spring.  Does that sound right?

 

Unless you have added a lot of weight to the bike the stock spring should work fine for you, but yes, I think lowering links do reduce the effective spring rate slightly.  Maybe bump up your preload a bit and/or increase damping?

[williestreet]

7 hours ago, Dave D said:

K-Tech 90 N/mm linear spring arrived. No local bike shops have a shock compressor. Soooo:

 

 

 

 

Had to super glue the metal collar to the pivot block to get it to stay at the top.

 

 

Spring size comparison. 90 N/mm obviously fatter.

 

 

I survived! Yay.

 

The whole thing wanted to flip over towards the handle end of the jack but some careful holding and keeping well back did the job. I will modify this so there is a brace each side to keep it all square to the jack.

 

The bike feels much nicer with my fat ass on it now. I am 89 kg's without kit. Height wise it is still very manageable. I had to fit 20mm lowering links and drop the forks a tad to get it comfortable. Feels more like a motorcycle now and less like a motorised bowl of custard.

 

I am in North Devon, UK, if anyone wants to use it.

Make a plate with a hole just bigger than the spring seat.  It will work better and reduce the risk of something hitting the shaft and doing damage.

If that slipped and the rebar hit the shaft it could easily scratch the chrome and you would need to replace the entire shaft or have it re-chromed.  

 

I have one using a small bottle jack and it works really well and is very safe.

 

 

 

[Uncle M]

4 hours ago, Endopotential said:

Nicely done!  I'm a bit of a lightweight at only 155lb / 70kg bare, but I'm surprised how bouncy the stock spring is.  Though I did lower the bike about 30mm, and I read that changing that distance adds leverage to the system and functionally makes the spring feel softer.  Any truth to that?

I'm thinking I'll eventually swap to a 85 N/mm spring.  Does that sound right?

@Endopotential before changing out the spring, measure your rider sag with you wearing all your regular gear. Rider sag should be approx. 30% of total travel. There should be instructions on how to measure correctly on this forum or probably on Youtube, or get it done by someone who knows what they're doing, like a suspension shop.

Edited February 23, 2023 by Uncle M

[Endopotential]

Thanks for the input you guys.  Yes, I definitely need to drag one of my riding friends into the garage with me.  We're always so hot to ride that I can never get them to stand at the side of my bike with a measuring tape.

 

I've got the preload nearly max'd out.  Just with the butt bounce it's pretty springy.  It's a nice cush ride on pavement; not too bad on bumpy dirt.  I'm just wondering what it'll feel like once I load it up with 30-40lbs of camping gear.

[Dave D]

12 hours ago, williestreet said:

Make a plate with a hole just bigger than the spring seat.  It will work better and reduce the risk of something hitting the shaft and doing damage.

If that slipped and the rebar hit the shaft it could easily scratch the chrome and you would need to replace the entire shaft or have it re-chromed.  

 

I have one using a small bottle jack and it works really well and is very safe.

 

 

 

Nice kit. That's the route I wanted to go down but no means of cutting such a big hole in the materials I have here. It was a case of "What is in the workshop now". Well noted about the chrome plating. I got away with it this time. Thanks for the info.

[Lewie]

12 hours ago, williestreet said:

Make a plate with a hole just bigger than the spring seat.  It will work better and reduce the risk of something hitting the shaft and doing damage.

If that slipped and the rebar hit the shaft it could easily scratch the chrome and you would need to replace the entire shaft or have it re-chromed.  

 

I have one using a small bottle jack and it works really well and is very safe.

 

 

 

 

Presume you could construct that out of some suitably strong timber and threaded bar/ bottle jack

[williestreet]

48 minutes ago, Dave D said:

Nice kit. That's the route I wanted to go down but no means of cutting such a big hole in the materials I have here. It was a case of "What is in the workshop now". Well noted about the chrome plating. I got away with it this time. Thanks for the info.

I didn't have a large hole saw either, but with some time it got done.

 

I drew a circle the size I wanted and then just drilled a bunch of small holes around the circle.  You want the hole 2-3mm larger than the spring seat. Then with a jig saw and a lot of patience connect the holes to cut the circle out.  Finish smoothing the hole with a file and it was done.  A real pain in the ass and it took some time, but it works very well.

 

 

Lewie I would never try to make one from wood because of the thickness needed to be strong enough.

When compressing the spring you need to compress it enough to pull the spring seat out the hole.  With mine I think you need to compress approx an inch or so to get enough room for removal and installation.

With wood the extra thickness would increase this significantly.  The more you compress the more thickness you would need because it needs to hold more and more load.

 

You could always make a plate of 2 pieces that bolts together to form a circle.  Might be easier to cut out 2 half moons than a circle and then a small plate that holds them together?

 

If you are a horder like me and you have a bunch of old rear sprockets laying around that you never threw out, check the hole size in the centre.

I was doing a spring swap on a different bike and didn't have the correct size plate.  I didn't want to make a new plate for just one use and noticed an old sprocket had a centre hole pretty close to what I needed.  Put the sprocket under one of my existing plates with a bigger hole and compressed the spring up against it.  Worked like a charm and saved me a few hours making a new plate.  Saved that sprocket for the next time.

 

Link to a video of how mine works.

 

 

 

[Lewie]

Excellent 

[AirborneSilva]

On 2/23/2023 at 11:35 PM, Endopotential said:

Thanks for the input you guys.  Yes, I definitely need to drag one of my riding friends into the garage with me.  We're always so hot to ride that I can never get them to stand at the side of my bike with a measuring tape.

 

I've got the preload nearly max'd out.  Just with the butt bounce it's pretty springy.  It's a nice cush ride on pavement; not too bad on bumpy dirt.  I'm just wondering what it'll feel like once I load it up with 30-40lbs of camping gear.

I just figured out my sag today with the help of DRC - ZETA Sag Checker since getting someone to help is not an easy task.  If I calculated things correctly after watching several videos my sag is 21% of full extension (with back tire off the ground), I'm currently 157 lbs or 71 Kg and losing.  I only had on shorts and t-shirt so with full riding gear I'd probably be still less than 25%.  With camping gear I can't imagine I'd be much over the magic 30% so a little more preload should do it.  Oh and my preload right now is only 3 clicks off zero. 

[Boondocker]

@williestreet Excellent! You probably spent less time making the shock compressor than I did using a floor jack and strap for a very sketchy and unsafe spring swap. I got it done but will never do it that way again. I will gladly copy your method. You made it look too easy!