Putting a suspension fork on a fixed fork bike

[rowan 46]

After a bad accident a couple of years ago. I had to give up my road bike as the position was too uncomfortable for my shoulder' I have recently started riding my Hybrid again but would like to put a suspension fork on. Partly for comfort and partly because I hang a dslr and a couple of lenses off the handlebars in a bag. Is it possible to do this without messing up the geometry too much or does it have to be a new bike? the bike I am riding is a Roux A8 it's not for off road but it will be used on towpaths as well as roads. Any advice is much appreciated

 

[Drago]

Unless the frames geometry is suspension ready you'll end up with a horrible blancmange.

 

[Pale Rider]

A cheap suspension fork is worse than useless, extra weight for no real comfort benefit over a quality steel fork.

By cheap I mean £100.

Pay double that and you might get something worthwhile.

Balloon tyres such as Schwalbe Smart Sam/Big Ben would be a more effective, cheaper, lighter and neater comfort upgrade.

 

[rowan 46]

Unless the frames geometry is suspension ready you'll end up with a horrible blancmange.

Thanks for the answer next stupid question is there a way of telling if it's suspension ready or is it an email to roux job?

 

[Drago]

I know little about Roux machines (someone here may well have the knowledge) so a quick email is in order. I'd be surprised if it was, and even then, like Paley says, you need to spend some proper folding.

 

[rowan 46]

Sorry the shock I was thinking of was either the RST vogue air or Rockshox paragon. I know Rockshox have the reputation but the Rst used to be used on all the top end german Hybrids it is more expensive but its lighter than the Paragon its more adjustable and I have used it before and Its a nice smooth ride

 

[Pale Rider]

Sorry the shock I was thinking of was either the RST vogue air or Rockshox paragon. I know Rockshox have the reputation but the Rst used to be used on all the top end german Hybrids it is more expensive but its lighter than the Paragon its more adjustable and I have used it before and Its a nice smooth ride

Sounds good to me.

The geo question might be hard to answer, the headtube angle may be OK, but it will also depend on length and height.

There's a risk when you bolt it all together the bike sits pointing upwards or downwards.

Having said that, it's possible to replace a sus fork with a rigid one, although I don't know if the rigid forks sold as replacements are standard, so the reverse may not be true.

 

[rowan 46]

Appreciate about the cash but The way I was looking at it a couple of hundred to basically upgrade a bike I like Is better than !500 for a new bike that has all the features I want So I am hoping that I can get away without spending that. Since my accident the bike is uncomfortable to ride more than a couple of miles if it really is impossible to do safely then its a question of flogging the bike for not a lot and saving a long time until I can get a bike I do like as much, with the same features but a quality suspension fork fitted but I am a bit afraid if I wait another year to get a new bike I may never get another bike again.

 

[Crackle]

If you are swopping forks the thing to look for are fork length and offset. Possibly the biggest change to handling will be getting the offset wrong. Getting a different length will alter the headtube angle by a degree for every 20mm difference. Longer will give you slightly less responsive but stabler handling and shorter twitchier handling. They're generalisarions though.

 

[Drago]

If you are swopping forks the thing to look for are fork length and rake. Possibly the biggest change to handling will be getting the rake wrong. Getting a different length will alter the headtube angle by a degree for every 20mm difference. Longer will give you slightly less responsive but stabler handling and shorter twitchier handling. They're generalisarions though.

Not to mention the changes to wheelbase and trail.

 

[Crackle]

Not to mention the changes to wheelbase and trail.

yep.

There is often or at least, can be, a certain tolerance, depends on how the bike was designed. The op will need to establish that.

 

[rowan 46]

Thank you all for the helpful answers. at least I have some idea of what questions to ask in my e-mail

 

[ChrisEyles]

You need to look at the fork axle-to-crown length, and the fork offset.

Fork offset is usually pretty constant around 45-50mm, and pretty much any new fork should be OK. Axle-to-crown length, on the other hand, varies from 390mm for a short-ish rigid fork to over 500mm for a longer travel suspension fork. As the name says, axle-to-crown is measured from where the wheel axle sits in the drop-out to the top of the fork crown where it sits in the bottom headset cup of the frame head tube.

Switching to a shorter fork will steepen the head angle and make the steering more responsive/twitcher. Switching to a longer fork (more likely if you're going rigid to suspension) will make the head angle slacker and make the steering more stable/less responsive.

I swapped the knackered old suspension fork on my 90s MTB for a rigid fork a little less than a year ago, going from an axle-to-crown distance of 455mm to 425mm. While the internet suggests this should make a significant, or at least perceptible, difference to the way the bike handles, I personally wasn't able to feel that much difference.

So from my experience I'd say if you can get a suitable fork with an axle-to-crown measurement within 30mm of the old one it's worth a go.

While I'd agree that a truly awful suspension fork is worse than a rigid one (that's why I made the switch on my old MTB after all!) I wouldnt' be too sneery about cheap-ish forks. I'd be happy to ride something costing £100 - but maybe not £30 new from ebay. Then again old 90s elastomer forks still feel pretty good to me (as long as there's no slop and play in the bushings making them flex all over the place). FWIW I do ride a modern bike with rockshox rebas (I think) quite regularly too, I'm just not convinced the difference is that earth shattering.

 

[ChrisEyles]

PS I spent *ages* agonising over axle-to-crown lengths, and even wrote a little piece of code to work out all the changes to head angle, wheelbase, bottom bracket height etc so this is a subject close to my heart Shame it turned out to make next to no difference to the handling, I was quite curious to see if it would!

 

[rowan 46]

my present fork has an axle to crown length of 400mm both the rst fork and the rockshox are 470mm so what do you think too much? I am thinking it is essentially going to be used as a flat barred touring bike so the extra stability may be handy with all the camera gear I carry