29er vs 27.5+ frame/fork difference

[Petero]

At some point in the near future I am looking at upgrading my ride - the 29" XC hardtail needs to go in favour of something more trail orientated.

While I am leaning towards something full suss, 29" with 120-140mm travel (6ft3 1/2 tall, 95kg) - the research has left a few unanswered questions in my head that I am hoping the learned crew can help with.

The idea of a bike that can switch between 29" wheels and 27.5+" excites me. But my question is this - If I purchased a specific 29" bike with boost, or a 27.5"+ bike, would these be interchangeable anyway given the similar OD? Understand that there would be slight geo changes but would these have much if any effect?

'preciate the responses.

PS. Any thoughts on using a scott spark 29" (120mm, 67.2deg head angle..) as a trail bike?

 

[The Reverend]

It's a nice position to be in at the moment. There are so many decent options.
Bikes like the Santa Cruz Hightower, Pivot Switchblade, Trek Fuel EX come immediately to mind.

I had a previous version of the Spark at 100mm and it was VERY capable given its travel. The new version or the Genius would be a great option.
Spend a fair amount time testing everything is all I'd say.

 

[Petero]

It's a nice position to be in at the moment. There are so many decent options.
Bikes like the Santa Cruz Hightower, Pivot Switchblade, Trek Fuel EX come immediately to mind.

I had a previous version of the Spark at 100mm and it was VERY capable given its travel. The new version or the Genius would be a great option.
Spend a fair amount time testing everything is all I'd say.

Thanks mate! Appreciate the input. The only difficulty I have is finding an XL frame to test out.

 

[ctguru]

Niner also a consideration

 

[stickso]

Depending on the geo, a 29er with a low BB might end up too low with 27.5+ tyres resulting in a lot of pedal strikes. Also, the size of the tyre affects this such as a 2.8" Maxxis not being as tall as a 3" Specialized tyre.

A 27.5+ bike is more likely to ride well as a 29er than the other way around.

Case in point is my Stumpjumper 6Fattie which is great as a 29er or with 27.5x3" Spesh rubber, but bashes the pedals way too much with 2.8" rubber. But for gravity stuff it's not an issue as I'm not pedalling

 

[Knuckles]

At some point in the near future I am looking at upgrading my ride - the 29" XC hardtail needs to go in favour of something more trail orientated.

While I am leaning towards something full suss, 29" with 120-140mm travel (6ft3 1/2 tall, 95kg) - the research has left a few unanswered questions in my head that I am hoping the learned crew can help with.

The idea of a bike that can switch between 29" wheels and 27.5+" excites me. But my question is this - If I purchased a specific 29" bike with boost, or a 27.5"+ bike, would these be interchangeable anyway given the similar OD? Understand that there would be slight geo changes but would these have much if any effect?

'preciate the responses.

PS. Any thoughts on using a scott spark 29" (120mm, 67.2deg head angle..) as a trail bike?

Ask JTmofo about his wonderful experience with his kona in 27.5+ guise...

 

[Sethius]

The spark 29 is our main selling trail bike that many of the folk use as a 140mm style bike in the end, id grab the spark 27.5 plus version and grab a set of boost 29 wheels for it personally. ( the plus wheels dont fit the 29 frame just fyi). Sparks more fun than the standard genius.

Re: testing where are you located?

 

[bmar560]

sorry to jump on here but I'm interested in the topic as well.
Switching from 27.5+ to 29er or vice versa will also need forks to match the wheels size correct ?

Or can you use the same forks for both 29er and 27.5+ ?

 

[Nambra]

A boost 29/27.5+ fork should run both wheel sizes no problem. Some manufacturers like SC suggest changing the air shaft to maintain geo, but it's not critical.

 

[The Reverend]

A boost 29/27.5+ fork should run both wheel sizes no problem. Some manufacturers like SC suggest changing the air shaft to maintain geo, but it's not critical.

OP, i hear you on demo sizes as I'm XL / XXL myself.

Pivot have this spacer designed to be placed between the bottom of the headset and crown on the fork to maintain HTA / STA. not sure if it can be purchased separately or if one could be machined? It's about 17mm in height IIRC.

 

[Daniel Hale]

the numbers you are looking at seem spot on to me, 120mm & 67-68 is great for trail, capable at XC but can be pointed down hil at less than DH trk's.

keep in mind the note what stickso said about BB height -I have a lapierre xr729 -which is their 2nd top xc bike but the bb is really low -I ran a 650b rear for a while while in the process of getting a new 29 wheel & even with 165 cranks I was hitting the cranks all the time [I'm 6"1']

few of the locals have the spec camber, pretty happy with it -I ride with a couple of bike shop guys who have the Norco sight/optics pretty happy with them,

 

[notime]

If your anywhere near the Blue Mountains you can have a pedal on my XL Fuel Ex, 29er only though. The 2018 models in soon have GX Eagle and pricing is improved.

I've not tried 650's on mine but the BB would be pretty low as mentioned. I've changed my fork air spring from 130 to 140mm and the pedal strikes significantly decreased.

 

[Petero]

Thanks for the input all.

Re: testing where are you located?

If your anywhere near the Blue Mountains

Thanks gents, unfortunately located on the West side (Perth).

Sethius, was very much considering the spark 720plus, but alas, no XL's left I believe.. Feel like I should have jumped on the 940 while Avantiplus had a one day firesale over this way.. (was down to $2.9k)