Thron2 6.9 fitment from 29ers to 27.5 and the flow on affects

[sparked]

So during Lockdown I bought a Thron2 6.9 - I couldn't test ride it but the LBS told me they'd happily work with me if the bike was too big.

Well it felt a bit too big. I initially asked them to just take the bike back for a refund but the Retail Manager talked me into trying a 27.5 wheelset on the bike. He told me they'd just done the same thing for another woman who also bought one and felt the bike was also too big for her. She allegedly loves it now.

I contacted Focus Australia and asked them if the Thron bikes were indeed compatible with the 27.5 wheelset and if they'd void warranty. I asked them 3 x and they ignored me. Not impressed given every other manufactuer ie Trek, Specialized and Merida here were more than happy to answer Q. Also worth mentioning that on the Focus website there is no mention that the Thron is compatible geometry wise with smaller wheelset. Only the Jam and Sam are I believe as they have the switch to alter geo.

So I agreed to the wheelset swap. They've replaced almost like for like DT Swiss H1900 wheels with E1900 and a lower profile Freedom Typhoon tyre. All up the bike is now 4cm lower and it does feel much more nimble to me and less erm big!

BUT during my first ride I noticed the pedal on downstroke feels VERY close to the ground. At first I tried to ignore this but that wont make it go away and last thing I want to do is have a stack on the bike because pedal has struck a bump in the ground! As you can see in this photo, the pedal is quite low (bare in mind some of this is the photo as there's a bit of bokeh in the shot) and I'm not even sitting on the bike.

I have emailed the manager and told him my new concerns. I half expect him to want to now change over to a shorter crank arm length (although I have said I want to return it).

What flow on impact will that have? I guess the saddle height now goes up as my leg will have more bend to it? Then that takes away some of the 4cm gain I won having the wheelset swapped over!

Thoughts?

It also looks a bit strange now too, so much gaps in the chainstay due to the smaller wheel diameter! I also lost those cool skinwall tyres but that can be rectified at another time.

 

[sparked]

So I've been reading this thread Pedal strikes - EMTB Forums

I think my Q is - what sort of clearance should I be aiming for with my pedal to ground clearance?

 

[Zimmerframe]

@Gary - Your Territory ? ..

 

[sparked]

@Gary - Your Territory ? ..

Go easy on me @Gary I'm a newbie!

 

[Gary]

lol

Firstly. The bike is NOT 4cm lower with the 27.5 wheelset. whoever told you that it was is probably not worth listening to at all.
With like for like tyre volume the difference in axle height between a 29" tyre and a 27.5" tyre is 19mm
Your Thron has a BB drop of 25mm. not massive at all for 130mm a 29er. but quite low for a 27.5 Eeb. But perfectly rideable.

My own 27.5 Eeb (Vitus ESommet 2019)has a BB drop of 25mm... but get this, it has 40mm more travel so technically has a far lower sagged ride height and *needs" 40mm more clearance when using full travel and I don't get pedal strikes.
Disclaimer: I do however absolutely love low BBs and have been riding far lower than this for years.

Not smacking pedals into obsticles is 100% down to the riders planning, skill and timing, it does take time to adjust and learn your ground clearance limitations. But once you have you will reap the rewards of stability and more grip (especially cornering) But I'm not even going to get into this here.

You are obviously a fairly short rider so could easily use 155mm cranks to regain 10mm clearance. This will have the bonus of allowing you to run a 10mm higher saddle and also a 10mm longer dropper post.

hope some of this helps

 

[Gary]

Out of interest. and if you happen to know, how much fork and shock sag are you running on the bike?

If you're a light weight rider it's tempting to run more sag so you feel like you're actually using more of the suspension. Try not to fall into this trap and stick with running somewhere around 20% on the fork and 25-30% on the shock (measured when stood centrally and evenly weighting both pedals, cranks level)
This will give the bike a more supportive midstroke and keep it from diving through travel or wallowing as you pedal.
when descending rough ground you should be aiming to keep your cranks fairly level (rearwards crank arm slightly rotated down) but even then you should be altering crank position depending on what obsticles you are approaching and whether you are cornering, riding a camber or riding in a straight line.

 

[sparked]

lol

Firstly. The bike is NOT 4cm lower with the 27.5 wheelset. whoever told you that it was is probably not worth listening to at all.
With like for like tyre volume the difference in axle height between a 29" tyre and a 27.5" tyre is 19mm
Your Thron has a BB drop of 25mm. not massive at all for 130mm a 29er. but quite low for a 27.5 Eeb. But perfectly rideable.

My own 27.5 Eeb (Vitus ESommet 2019)has a BB drop of 25mm... but get this, it has 40mm more travel so technically has a far lower sagged ride height and *needs" 40mm more clearance when using full travel and I don't get pedal strikes.
Disclaimer: I do however absolutely love low BBs and have been riding far lower than this for years.

Not smacking pedals into obsticles is 100% down to the riders planning, skill and timing, it does take time to adjust and learn your ground clearance limitations. But once you have you will reap the rewards of stability and more grip (especially cornering) But I'm not even going to get into this here.

You are obviously a fairly short rider so could easily use 155mm cranks to regain 10mm clearance. This will have the bonus of allowing you to run a 10mm higher saddle and also a 10mm longer dropper post.

hope some of this helps

Thanks Gary. Helps a lot.

His 4cm calculation included the change of tyres as the new tyres replace the high profile Maxxis Rekon 2.6 3C EXO TRs it came with. I can see the bike is much lower than it was when sitting on it and even where I store it and where the HB lean - it’s quite lower.

When you are new to bikes, it’s pretty easy to be led astray by convincing shop folks. That was my main concern - given they dropped nearly $1k Aussie on new set of DT wheels knowing they won’t get that return on the old ones, there’s obviously lots of profit in this bike.

 

[Gary]

The change from a 2.6" Rekon to your current 2.25" volume tyres will probably account for a further drop of around 7mm Definitely less than 10mm nevermind the 21mm the bike store guy estimated.
a change of tyres to a volume of say 2.4 or 2.5s would minimise this down to just a couple of mm.

 

[sparked]

Out of interest. and if you happen to know, how much fork and shock sag are you running on the bike?

If you're a light weight rider it's tempting to run more sag so you feel like you're actually using more of the suspension. Try not to fall into this trap and stick with running somewhere around 20% on the fork and 25-30% on the shock (measured when stood centrally and evenly weighting both pedals, cranks level)
This will give the bike a more supportive midstroke and keep it from diving through travel or wallowing as you pedal.
when descending rough ground you should be aiming to keep your cranks fairly level (rearwards crank arm slightly rotated down) but even then you should be altering crank position depending on what obsticles you are approaching and whether you are cornering, riding a camber or riding in a straight line.

sag is at the 30% range by my calculations. The LBS asked me weight and dialed it in. Due to Covid lockdown they haven’t had me actually test the sag. But I’ve seen lots of videos and we have checked it at home.

Yep cranks level for the downhill rough stuff and cornering- all good there been doing that a long time. The ascending over the bumpy stuff will take lots of practice and I accept that

tonight I’ll get my partner to help measure the actual pedal cleadance I have whilst sitting on the bike. Then hopefully restrictions will ease and I can actually goin for a bike fit.

 

[sparked]

@Gary thank you so much. Hopefully my Q and your answers might help out someone else as well!

and thanks @Zimmerframe for tagging G

 

[Gary]

No worries
I wouldn't bother paying for a bike fit for mtb TBH.
unlike road far too much comes down to personal preference and personal comfort.
Efficiency wise you still want to get your max saddle height correct and you don't want to be too cramped or too stretched on the bike but unlike a road bike altering stem length, bar height, width etc. alters the bike's handling more than it changes the riders efficiency or comfort.

happy to help you with advice on the basics of setting it up if you need it.

 

[sparked]

No worries
I wouldn't bother paying for a bike fit for mtb TBH.
unlike road far too much comes down to personal preference and personal comfort.
Efficiency wise you still want to get your max saddle height correct and you don't want to be too cramped or too stretched on the bike but unlike a road bike altering stem length, bar height, width etc. alters the bike's handling more than it changes the riders efficiency or comfort.

happy to help you with advice on the basics of setting it up if you need it.

An update!

I ended up returning this bike for a refund. The Monday after these posts were made it occurred to me that if I could have sat on this bike in the shop and spent 20 mins with it, I would not have bought it. So based on that, I just gave up on it.

And I felt much better once I did that.

Sometimes some things just dont feel right. I also found the shop was telling me some stuff that made no sense/wrong for eg "the sag makes no difference to how low the bike goes when you sit on it" ummm thats just plain incorrect. I couldn't be bothered with them after that.

Still shoppping.....