Has anyone with a jam2 29er ever swapped their wheels and forks out for 27.5 version to see if it rides better?

[Billybopsbasher]

Basically as above....

I have a whyte g160 that I can take the wheels and 170mm yaris from to convert my 29er version into the plus size tyre version(from the research I've done the mainframe is the same anyway... Just the rear end is longer to accommodate the larger rear wheel).
The reason I'm considering this is to try and combat the horrendous brake dive that the standard recon rl has and to lower the stance a bit.... With some 152mm cranks.

Can anyone give real world experience on this?
Cheers in advance?

 

[steve_sordy]

Nope, I haven't tried that. I test rode the version with 27.5" x 2.8" tyres and went for the 29er with its 2.6" tyres, now 2.5".

As for the horrendous brake diving, I'm 92kg in my riding kit and I don't suffer from that on my Revelation RC, even with the compression damping fully off (although I ride with it 2 clicks back from fully off). One bike I did have that suffered from brake dive was the YT Capra (Pike RCT3) fork. Adding some tokens to the air spring sorted that out. Cheap and quick to do. Does your Recon have the capability to add tokens? If you are not sure it would be well worth finding out as it has a big impact.

I get on just fine with the 165mm cranks and the 20mm BB drop.

 

[Billybopsbasher]

Nope, I haven't tried that. I test rode the version with 27.5" x 2.8" tyres and went for the 29er with its 2.6" tyres, now 2.5".

As for the horrendous brake diving, I'm 92kg in my riding kit and I don't suffer from that on my Revelation RC, even with the compression damping fully off (although I ride with it 2 clicks back from fully off). One bike I did have that suffered from brake dive was the YT Capra (Pike RCT3) fork. Adding some tokens to the air spring sorted that out. Cheap and quick to do. Does your Recon have the capability to add tokens? If you are not sure it would be well worth finding out as it has a big impact.

I get on just fine with the 165mm cranks and the 20mm BB drop.

What made you go for the 29er over the plus version bud?
The brake dive is normal for the cheaper rockshox.. I'm quite a lot heavier than any of you lightweights ?.
I can also feel a bit of flex when I corner hard (even with the spoke tension increased) compared to my whyte(obviously?‍)
It was just a thought as I already have the spare parts that's all but best to ask incase I came across any horror stories

 

[Gary]

Recon's are a pretty basic cheap fork. to counter brake dive with them simply run higher air pressure (less sag).
TBH Yari's will dive just as badly if not set up with enough pressure. The two forks share pretty similar damping technology. But (newer) Yari's have quite a different air spring curve.

 

[steve_sordy]

What made you go for the 29er over the plus version bud? .....................

It was the 140mm travel 2018 Jam2 6.8+ that I test rode. (ie 27.5 x 2.8). Once I'd got the bike set up to suit me and sorted the tyre pressures, it was the most fun emtb I had ridden after having ridden 7 different ones before. It was the first one where I could forgot it was an emtb and just rode it for the fun. So I was convinced about the Focus Jam2, but which bike to ride? I couldn't get access to ride a 29er, and I wanted the 150 travel of the 2019 model, so I had to make a decision that was not fully informed. I didn't like the weight of the 2.8" tyres and I had a hankering to have a 29er. I'd ridden clockwork 29ers on test days and followed behind my mates on theirs and observed the differences between them and my 27.5er. It was a close run thing I confess. But the choice of a 29er was a leap of faith. I confess to wavering and almost changed the order back to a Plus. But I'm glad I stuck with the 29er. My next emtb will be a 29er or a mullet.

 

[YorkshireDan]

Does your Recon have the capability to add tokens?.

Ive got the 2019 recons on my jam2, they’ve changed the design so you can’t put the threaded 32mm tokens in, unless I’m missing something. The cap isn’t threaded, it sits into the top of an ally tube inside the fork leg

 

[Gary]

Adding tokens to a fork only reduces the air spring volume. That's it!
Reducing air spring volume means the spring rate ramps up more the further into the travel the fork is.
ie. the fork will become increasingly harder to compress the deeper into it's travel it is.
The flip side, and the entire point in tokens is to allow a rider to run more sag and a softer initial spring rate for better small bump response with that ramp up reducing excessive bottoming of the fork.
Tokens don't reduce brake dive.
INCREASING AIR PRESSURE (ie. LESS SAG) REDUCES BRAKE DIVE.
As does INCREASING LOW SPEED COMPRESSION.

If you're having to increase pressure excessively to hold a fork up you actually want LESS tokens and a more linear spring curve. Otherwise you won't be achieving full travel.

 

[Billybopsbasher]

Well... I had a spare couple of hours so I had a go at it?
Changed the 29er recon 140s to yari 170s and that made a massive difference in front end stiffness and contrary to what Gary has said(no idea why as what he said should be correct) the forks have exactly the same pressure and held up much better in the travel than the recons.
Now I haven't got any plus size tyres so used what I had which where a minion 2.35 front and a minion semi slick 2.3 on the rear..immediately I could notice the difference in seat and bar height but it didn't detract from the ride.
The wheelbase was exactly the same at 1230mm
The bb height has dropped by 17mm approx so shorter cranks would deffo be needed if I was to stay like this.
All in all it made the bike feel more manoeuvrable and agile (pulling manuals and wheelies etc).

 

[Gary]

contrary to what Gary has said(no idea why as what he said should be correct) the forks have exactly the same pressure and held up much better in the travel than the recons.

dude.
That's not contrary to what i said at all.
170mm Yari's have a completely different air volume AND spring curve to your old shorter travel Recons. Your settings are not (directly) comparable
The fact you're running the same pressure in both is nothing more than coincidence.
glad it's worked out for you.
I love low slack bikes.
Even with the extra 17mm BB drop it's not all that low for a 140mm travel frame. should rail turns now. Just learn to plan ahead more and resist the temptation of pedalling blindly at stuff. mtbs are often faster pumping/tucking than pedalling anyway.

 

[Billybopsbasher]

dude.
That's not contrary to what i said at all.
170mm Yari's have a completely different air volume AND spring curve to your old shorter travel Recons. Your settings are not (directly) comparable
The fact you're running the same pressure in both is nothing more than coincidence.
glad it's worked out for you.
I love low slack bikes.
Even with the extra 17mm BB drop it's not all that low for a 140mm travel frame. should rail turns now. Just learn to plan ahead more and resist the temptation of pedalling blindly at stuff. mtbs are often faster pumping/tucking than pedalling anyway.

Ahh?.... I stand corrected then... Id read that they having a similar damper that they should react similarly (dependant on air pressure) so was slightly confused that even though the yari having a larger internal volume (purely guessing due to stantion diameter) I ended up with nigh on identical pressure in each. Logic to me would suggest that given the same pressure on both that the yari should be easier to compress (like having a large air can on a rear shock instead of a small one)
Already looking at shorter cranks... 155mm purely due to 152s being sold out.. If it rides nice like it then I'll shell out on some wider rims and larger volume tyres ?

 

[Gary]

The Dampers have absolutely nothing to do with the air spring, Air volume, suitable pressures or air spring curve.

Logic to me would suggest...

Stop comparing them .You're just confusing yourself even more.
a 140mm Yari and 170mm Yari will have completely different air spring volumes and spring curves and each travel change (New air shaft) requires different pressures to achieve similar sag/travel. Then you have the various air shafts (Debonair etc.) and varying negative chamber sizes that alter it even more. Nevermind trying to compare a 32mm stanchion 140mm Recon to the 35mm stanchion Yari/Lyrik chasis.

Have a read of the suspension guide I had stickied in the general EMTB forum. All you'll ever need to understand your fork is in there.

Wide rims, super short cranks and big marshmallow tyres pretty much ruin what you've achieved with the new lower and slacker geometry you've created. Mainly with regards to the (now) lower COG and better cornering traits... But... oh... well... at least it was nice for a little while

 

[Billybopsbasher]

Marshmallow tyres?... I was merely going to fit a minion dhf 2.5wt tyre up front and a dhr 2.4wt out back that's all... And just to give them a bit of stability was considering some wider rims than the wheels currently have(mavic 624) hardly going to ruin it methinks. How does having shorter cranks ruin it also... I can't think of any way they would... They'd purely be for negating pedal strikes but I appreciate the info regarding the forks?