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29er hardtail build. Fork, brake & tyre advice please

Cotic Tony's picture

By Cotic Tony - Posted on 17 December 2011

NB: Originally posted elsewhere on the Global Riders Network and appears via syndication.

Hi All
I'm about to build myself a modest 29er hardtail using a new frame, fork and wheelset plus a heap of old cast offs.
If you are running big wheels at the moment I am interested in your views on the following:
1. With the bigger wheels & weighing 85kg would I be better off using 180 discs than 160s? (XT brakes)
2. I will be using an old 9 speed 42,32,24 - 12-34 gear set up. What would you recomend as a good 29er gear spread? I was considering a 2 x 10 set up.
3. Do the same tyre combinations work for 29"? If so I'll probably stick to Schwalbe or Maxxis.

Feedback appreciated.

Slowpup's picture

This tread is useless without pics! Smiling

I'm not sure that my experience tyre wise will be relevant but...

1. I'm about your size, and if you are running XT brakes from the last 3 model years my experiences would say 160 rotors will be fine. I run hope X2 calipers with 160s on my 29ers and the only time I've thought about bigger rotors was at the shuttle pick up in Rotorua. Not because my brakes weren't up to the job, just because I'd been on and off them so much in the preceeding 10 minutes. The recent XT brakes have heaps more power than the X2.

2. I'm running a 1x9 32/11-34 and would really like a 12-36 for that bail out, but then my other bike is set up as SS 32/19 and I tend to avoid hills like herpes. If it's all gear that you have sitting around you could suck it and see? The difference in low gear between a 26" bike with 22/34 versus a 29" at 24/34 is only about 20% harder pedalling when you have a gear spread of 495%. Going to a 22/36 on the 29er will be about 5% harder than the 22/34 on the 26er..... If you are happy with the gearing you run now, why not chuck the details into a gear calculator and see what you lose/gain with the proposed 29er set up? has pages of info and tools.

3. I run completely different tyre combos on the 29ers to what I ran on the 26" bikes... but I find that over here the Racing Ralphs f/b are great in almost any condition. 29x2.4 front and rear at 20psiF/24psiR gives excellent traction on our sandstone trails and tends to float over sand and gravel. The only places I find they lose out is slippery mud....which I gather isn't such an issue out your side of the island. I run tubeless and with widish rims (24 mm on the hardtail and 35mm on the rigid)

You asked for fork advice in the title.... if you still have the option to choose....tray and get a QR15. The big hoops can really twist up the front end in techy terrain. Though I've never cursed my 9 mm QR, I notice the difference in steering precision between the 100x9mm on the pogo stick and the 135x9mm on the rigid..... a lot of that could be down to the difference between rigid and suspension, and I've never done a back to back comparison between a 9mm and 15 mm axle on a 29er. The 15 mm axle on my 26er was like a revelation in stiffness and steering directness, and I can only suppose it would be even more apparent on a 29er.

Have fun building and tinkering.

DudeistPriest's picture

I mainly ride XC and on my 29er I run the following (I'm 84kg):

XT brakes on 160 rotors, plenty of stopping power, I wouldn't go bigger
2 x 10 38/24 chainrings
Cassette 11-36t

Low gear has a similar feel to granny gear on my 26er (11-34, 22/32/44). Only issue I have with my set up is I tend to run out of gears at the top end when riding really hard, however, who rides flat out all the time so not a big issue really.

Tyres I muck around with all the time depending on conditions. In the main I run tubeless 2.0"

hawkeye's picture

I don't have a lot of 29er experience, it being limted to about 3 months on a belt drive steel-frame singlespeed.

However, I'd encourage the use of a 15QR front end if you can. My first roll-through down the rocks by the Hydro Lab at Manly Dam on a 9QR Rockshox Reba dual-air resulted in a comical over-the-bars, because unexpected flex in the steering made me miss my intended line by a couple of centremetres. I liked the fork otherwise and next time around I knew what to expect, but stiffer, less flex-prone steering would have been more confidence-inspiring.

Better still - if you can afford it - is a Lefty. A second-hand 140 or 130mm fork of recent vintage can be fitted with 40mm of travel-reducers quite cheaply to stop the tyre contacting the steerer, and you will have the gold standard in 29er steering precision. This is a very popular option in the US now that Project 321 adapters are available to enable Leftys to be fitted to any bike.

Cotic Tony's picture

Cheers guys. I've gone for 160 & 180 Icetech XT rotors as I already have an adaptor & there was only $5 for the bigger disc.
Despite wanting a thru axle I found a great deal on a Fox Float 100 2011 rlc so hope that it won't disappoint. Maybe the 35% off tempted me as I run 15 thru on my other bikes & am a big fan although with only 100mm & decent wheels on this one I thought that it would ok. Will report if not.
Gear wise I'm going to fit my 9 speed then see.
With tyres I worry that the big 2.4s will exacerbate flexibility in the fork so am temped to go for a 2.25 like the Maxxis Ardent, Ralph or Specialized Captain.
All the best. T

Lach's picture

I've got a 36t on the rear as, from the little I understand about gearing ratios, this is about the same as having 34t on a 26er. I'd need a bigger one again if I went to 2 rings up front...

Slowpup's picture

I feel the 2.4's isolate the fork from a lot of the features that exacerbate flex in the fork. They fit fine in the F29RLC100, but you'd need to check frame clearance at the rear....

The fatter tyres tend to float over rather than dig in for instance on sand.

I don't really notice any difference in grip or competence between the 2.4 on the rear of the HT and 2.25 on the rear of the rigid. Theoretically I should run the 2.25 on the HT and 2.4 on the rigid but....

Sounds like you're all set Tony. Don't forget to post pics.

Oldernslower's picture

Had 2 29rs. Depending what spider you have on will determine what gears you can use without modifying the spider. A 29r is approximately 11% higher geared than a 26r with the same gears.

To get the same gearing as a 26r (revs*speed) with 24/32/42, you will need 20/30/40 which I've used for a couple of years on 4 arm spiders. These front rings give almost the same gearing as a 26r. Middleburn are now making these rings for the 29r. Except they are only available for a five arm spider. They consist of a 20T Inner, 30T Slickshift middle, 40T Slickshift outer and are for a 94/58mm 5 bolt pattern spider only. (see )

The 20/30/40 gives 16 unique gears (on a 10 speed), 24/38 gives 13 unique gears, 22/38 gives 14 (if within 1kph of each other gears are no considered unique). Gearing is a personal thing so it depends on strength, riding style, terrain, etc. I've tried 2*10 (20/36 front rings, also tried a 20/33 setup) and loved both - except I run out of top end on long downhills, and the jump from 20 to 36 needs a lot of down/up shifts (4) at the rear. So now going back to 20/33/40 on my 4 arm spider. I also need low gearing to get up hills Sad

If you don't use the granny ring on your 26r then 22 or 24 front small should be ok on a 29r and a 38 Front large will give same speed as a 44 on a 26r. (speeds are worked out using the radius of a compressed tyre, not its rolling circumference)

Many 2*9/10 front derailleurs have a claimed 15 tooth capacity (hence why they use 24/38), however this is a guide and I've used them with 16 teeth spread (20/36) with no probs.

My suggestion is, if you have to buy front rings get the cheapest (or second hand ones) you can find and try them out, once you settled on what suits you then buy good quality ones. Your LBS or people on here may have old but useable front rings they could lend you. If you really need low gearing then get a 9 speed 12*38 or 39 cassette from Action Tec ( )

Tyres:- Hate fast roller tyres on pea gravel, for me the tread is too shallow - but thats just me and probably due to a lack of skill Sad. So I use tubeless F&R, Specialised Captain on rear, Purgatory on front. Find these good for me - except in deep gravel when the aggressive tread on the captain tends to dig itself in bit Sad. So the question really is which Schwalbe or Maxxis tread suits you?


Cotic Tony's picture

Thanks for all of the info guys, it's been logged in in a slightly less technical form.
Tyre wise my first set will now be Maxxis, Ardent UST front & Crossmark UST rear. This is only because a mate gave me the Crossmark after ordering it in error & I found an Ardent for $39. Maybe not race tyres but from experience they should at least work ok.

Gear wise I almost never use the granny gear on my HT so am tempted to try 22 - 34 on the front with a 12 - 34 cassette running 9 speed as I have the parts already.

BTW. I just fitted the latest XT calipers to a mates 26" Duallie tonight in place of some cheap Hayes units. Instant 100% improvement in stopping power but I still prefer the solid feel of my Hopes.

Will definitely put pics up.
Cheers T

Slowpup's picture

+1 for the Hopes Eye-wink

hawkeye's picture

When you say fitted XT calipers, do you mean the entire brake set including levers/master cylinders, or just the calipers?

Reason I ask is that Shimano use mineral oil and Hayes use DOT brake fluid. Each fluid will cause the seals in the other brand's hardware to fail... and that failure is guaranteed to happen exactly when you *need* maximum braking effort. Sad

Mixing Shimano and Hayes, or Shimano and Avid bits on the same brake system is not recommended.

Hoping you meant you changed the whole brakeset Smiling

Cotic Tony's picture

What can I say. He's Italian & insisted on the best virgin olive!

Seriously though what I meant was that we fitted the latest XT brakes but used his existing 160 rotors. I have Ice-tech rotors on the way for myself but he's a tight ass and is very happy with the upgrade.

I also notice that the latest XT shifters are offered in a clampless (iso/ist?)package to mate up with their brakes. Has anyone done this?
Hope/XT matchmakers are great & place the controls in exactly the right spot as well as reducing bar clutter.

Can't ride at the moment due to a dead leg that's so bruised it looks like a horse kicked me. This was sustained after an over the bars endo at the end of Kamikazi. I'd done all of the good stuff, took a suck on my camelback and rode straight into a 10cm Blackboy!!! I'd only been riding 20mins so tried improving my skills on the Lancaster run rather than ride Rocky etc. Painful but great fun...

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