Changing forks. 29" sus 63mm travel to 100mm UPDATE RESULT

[deliquium]

Thanks all for your replies and the relevance noted of my personal use and style of cycling - as opposed to what the possibilities and limits are of the various components.

Basically my idea of 'off road' cycling is gentle 'gravel' bumbling - drops, rocks and puddles are for other more adventurous souls

I've found some axle to crown figures asked for - assuming them to be correct?

Cube One head angle 69.5º with Suntour NXV30 63mm travel/492mm axle to crown/46mm offset = 89mm trail?*

Cube Performance head angle 68.5mm with Suntour NVX30 100mm travel/492mm axle to crown/46mm offset = 96mm trail?*

Rockshox Judy Silver 100mm travel/509mm axle to crown/42mm or 51mm offset available.

*according to http://yojimg.net/bike/web_tools/trailcalc.php as a suggested resource upthread

[rareposter]

Basically you're getting an increase of 17mm in fork length. (509mm - 492mm)
Knock off 10mm to account for sag, it's 7mm longer. Less if you go for a bit more sag (ie a more supple fork).

Maybe a third of a degree change in head angle which I'd suggest is pretty much unnoticeable.

So yes, the fork will be fine as a replacement, 42mm offset.

Just check that the steerer tube is the right dimensions, there are all sorts of tapered gauges now so drop the old fork out and measure everything so you can get a direct replacement.

[531colin]

……..
Basically my idea of 'off road' cycling is gentle 'gravel' bumbling - drops, rocks and puddles are for other more adventurous souls
……..

How about a nice simple lightweight rigid fork for that sort of use?
Suspension forks of any sort are really for “big hits”, tyres are better for small rumbles.
Fascinating that suspension forks are a marketing essential for touring flat bar e bikes which sit the rider bolt upright with very little chance of ever getting any weight on the front wheel.
Be interesting to put a zip tie round the existing fork to see how much travel you actually get on a ride

[rareposter]

Be interesting to put a zip tie round the existing fork to see how much travel you actually get on a ride

If they're as non-functional / broken as the OP suggests, I reckon "zero"

This is one of the major problems with entry-level bikes, hybrids, flat-bar tourers and especially kids bikes etc. They're sold with suspension forks because marketing. They look cool, it's a "feature". Everyone - even non-cyclists - know that suspension = comfort. And everyone wants to be comfortable on a bike.

Problem is that the forks supplied are invariably crap. Or at best they're "budget". They'll work for a bit (like in the showroom) then they'll get water in them, seize up and they're too cheap for anyone to bother making spares for them so they go on for ages as near rigid forks.

Actual decent suspension forks with a degree of adjustability via an easy air apring can be transformational to comfort and control and the overall rideability of the bike. BUt obviously it's quite an expensive up-front purchase also involving complexities like fork length, steerer tube dimensions, geometry plus specialist tools to fit the headset so it's an upgrade / improvement that few people ever make.

Same way that many cheap bikes are sold with terrible cable disc brakes, they never work properly so the buyer just assumes that all disc brakes are crap without ever upgrading to a decent set that hugely improve ride comfort and safety.

[Cowsham]

……..
Basically my idea of 'off road' cycling is gentle 'gravel' bumbling - drops, rocks and puddles are for other more adventurous souls
……..

How about a nice simple lightweight rigid fork for that sort of use?
Suspension forks of any sort are really for “big hits”, tyres are better for small rumbles.
Fascinating that suspension forks are a marketing essential for touring flat bar e bikes which sit the rider bolt upright with very little chance of ever getting any weight on the front wheel.
Be interesting to put a zip tie round the existing fork to see how much travel you actually get on a ride

Exactly what I'm trying to do even though my existing Rockshocks are probably as good if not better than the ones deliquium is upgrading to. Although the travel is 100mm the a 2 c is only 470mm ( 27.5" wheels ) and it's quite difficult to find a suitable rigid fork. I think I've found one but not ideal as I want lugs for panniers too and the new ones don't have that.

[531colin]

Lee Cooper ( for example) will build whatever you want, in steel of course.

[Cowsham]

Lee Cooper ( for example) will build whatever you want, in steel of course.

I'm kind of leaning ( pardon that please ) towards the exotic brand -- they've aluminium and carbon but both will still need my P clips ( cos they're just round pipes / stanchions ) to mount the rack which I'm not too worried about but just would be nice to have built in lugs.

[531colin]

Not sure about P clips on carbon?

Spa have a couple of carbon forks on their website, gravel or adventure(?) with lots of mountings for “anything “ cages; probably too much to expect they can be used for a traditional front pannier rack?

[Cowsham]

Not sure about P clips on carbon?

Neither was I but the spec says the carbon fork is actually radially stronger though I still have my reservations.

Spa have a couple of carbon forks on their website, gravel or adventure(?) with lots of mountings for “anything “ cages; probably too much to expect they can be used for a traditional front pannier rack?

It's the 470mm axle to crown distance that's difficult to find in a rigid fork along with a 1 1/8 straight steerer and non through axle and lugs etc etc and post mount caliper ( although I can buy an adaptor to convert from IS to post mount )

[Jezrant]

@ Cowsham: Kona?
https://www.konaworld.com/en-uk/product ... atte-black
I was also thinking of an Orange fork like that but not sure of the a2c. A 'wanted' ad might turn up others.

auto-.correct keeps changing your username into cowshed!

[deliquium]

Basically you're getting an increase of 17mm in fork length. (509mm - 492mm)
Knock off 10mm to account for sag, it's 7mm longer. Less if you go for a bit more sag (ie a more supple fork).

Maybe a third of a degree change in head angle which I'd suggest is pretty much unnoticeable.

So yes, the fork will be fine as a replacement, 42mm offset.

Just check that the steerer tube is the right dimensions, there are all sorts of tapered gauges now so drop the old fork out and measure everything so you can get a direct replacement.

Have just measured the Suntour NVX30 forks, as opposed to reading the dimensions off their website - and axle to crown is 488mm, not 492mm as assumed

(a further delve into the Suntour website does list a "cross" (assume as in cyclo?) 29" x 63mm travel fork with the 488mm a to c)

I do have a new unopened boxed pair of RS Judy Silver TK 509mm a to c and 42mm offset, just delivered - am now wondering if a pair of 51mm offset Judy's will be more suitable? Will I be able to detect the difference with my gentle style or riding anyway?

Darned ignorance

[Brucey]

...Suspension forks of any sort are really for “big hits”, tyres are better for small rumbles....

FWIW a very long time ago, I was driven to make my own fork internals. I did this twice only, starting with RS Indy S and RS Judy SL respectively. My preferred solution was to have rising rate springs giving ~4" travel, in conjunction with variable rate dampers, ideally in both legs. Because the forks basically never get very hot, I thought it might be possible to make variable rate damping valves using rubber and plastic parts where 'normally' (in car/motorcycle dampers) there would be metal. So I set to, and before long I had built probably the World's only set of RS Indy S forks with ~100 mm travel and open bath variable rate dampers. I found this conversion very easy; all my mad ideas worked, and worked perfectly.
Emboldened by my success, I started work on the Judy SLs. I soon wished I hadn't; for some reason everything seemed a lot less easy. I eventually prevailed, but only after I'd taken the oily fork apart so many times that I gave myself dermatitis for the first time. Maybe I was being fussier or something; however, the work was also more complex, so maybe that had something to do with it too. I did so many miles on that fork that I wore the stanchions out, and had to have them Keronite treated. Thus treated, it turns out that they are hard enough to wear the bush backings down too, despite copious lubrication. Although I have fresh bushings to go in, I don't think this is the answer, because they may still wear, and in addition the Mg alloy lowers are slightly corroded. Currently the plan is to ream the old bushings to size and then to bond some kind of liner in, probably 0.25 mm brass.
Both the forks I converted had excellent small-medium bump performance (in stark contrast to how they were originally) leaving the tyre to deal with the really small stuff eg. the road surface. Plush? Nothing else even came close, (initially) softly sprung with low speed damping that reminded me of an Ohlins-suspended motorcycle.

[Jezrant]

One thing that RS have improved is the plushness. The RS air forks are now plusher than they were 10-15 years ago. Not Fox plush, but getting closer. But I agree, tyres make more of a difference for little surface bumps, hence my suggestion to try lowering the tyre pressure first on a tubeless setup.

[rareposter]

Have just measured the Suntour NVX30 forks, as opposed to reading the dimensions off their website - and axle to crown is 488mm, not 492mm as assumed

Still only 21mm height increase.
Run the fork with 12-15mm sag, that's back at 10mm difference, half a degree on the head angle.

It'll be fine.

Plus at full compression (something your current forks won't do!) the head angle will be effectively steeper (for a short time) anyway.

[Brucey]

if you want a steel fork with rack mounts and a2c of 470mm, the easiest way might be to take a longer set and then do a cut and shut job on them. If a slash cut joint is used, about half way down, the highest stresses on the joint will be avoided and the tube, being (usually) parallel-sided at that point, has an external dimension that is easy to match up which can then be dressed prior to paint. If the 'burst' welding strategy is also successfully deployed, the weld could have good toughness too. Forks can break at this point, but IME unless damaged in some way, a failure at this point in a steel fork tends to not happen very quickly.