[Closed] 29er geometry - some specific questions about forks/frames and fast handling...

29erhater aboard 29er he likes shock!:

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Wide bars FTW 😉

how does the offset affect the handling then? is it just down to the wheelbase length?

ADH - he liked the bike - he is now going to build up a bike he really doesn't like as punishment for his personal failing - his own big-wheeled sack-cloth and ashes!

LOL - well, sort of TooTall 😉

I liked it but that unfortunately doesn't mean that I can have it. As such, I want to see if I can get what I want a different way. Unless you fancy buying me one, TooTall...

More offset (aka rake) makes for faster handling (reduces trail)

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http://www.tonyfoale.com/Articles/RakeEx/RakeEx.htm

http://www.rbracing-rsr.com/rakeandtrail.html

Clubber - My first 29er was a Viper (bought it 18mths abo) and it was run with 100 mm Manitou Minutes. Previous to building the 29er i was riding a BlurLT and to be honest i didn't notice too much difference is handling in the twisty stuff but i have put that down to steeper angles and a bolt through fork as opposed to a qr on the blur. However I've since owned a Swift & currently a Paradox.

The Swift with the same forks on it was better in the tighter stuff but felt a bit compromised when pointing downhill as the standover height was less than it was on the Viper. It did handle quicker and was more fun to ride but i think thats because the top tube on the Viper was longer than on the Swift even with a 70mm stem.

I have to say that the Paradox handles most like a 26er as its got slacker angles and shorter chainstays than either of the other 2 but then its 4x the price of the Viper as well.

In short, the Viper with that set up is not going to be the quickest handling machine in the world but then i have come to realise over the past 18 mths of riding 29ers that they do need a bit of manhandling, or maybe thats just my "special" riding style 😳

Thanks for that - how was the Viper btw? What was the mudroom like around the chain/seat stays? Just wondering if it'll fit a 2.3 ok.

Have you seen a 2.3 on 29ers? It is an awful lot of rubber. 2.2 and you'll be reet.

bigsi - you reinforce my belief that you get more out of a bike (regardless of how slow you think the steering etc is) the longer you ride it. There is something different about riding a bike that actually fits rather than riding what is almost a bmx - subtle but it sounds like you get it now with the bigger wheels.

I ran Spesh "The Captain's" in 2.0 during the summer and then Bonty ACX's in 2.2 when it got a bit soggy, never noticed clearance being an issue so guess it must have been fine.

I've never had any issues with the bike/frame etc other than the paint is waffer thin so protect it where ever you can, chainstays are a must.

I don't know how much you are paying for yours but i paid £125 new off of CRC and was/am very happy with it. In fact its currently resting against the office wall behind me as its now my commuter.

A good first foray in to the murkey world of 29ers if you ask me but you'll be wanting a Swift before too long, and yes the Swifts work really well with a 100mm fork 😉

Too-Tall. Yep, i no longer own a small wheeled bike and hated the one's i tried on my lbs demo day.

All the guys a i ride with say i ride better on a 29er than i ever did on a 26" wheeler and it doesn't look like a 29er next to me. One guy on a 26" even offered me one of his spare inners when i punctured that Thursday and i had to point out that it wouldn't fit. He was mistified till i explained to him i was on a 29er. 😆

The 26" inner tube fits fine - I ran my bike for 2 years on 26" inners - you just need to stretch them a little bit before inflation.

Ah, good point - 2.2 it is then 🙂

clubber - just seen your post on rd's forks. I wouldn't go longer than 100mm on a Viper frame if i were you. I think it will handle real odd with 120mm.

It's just my opinion but the Viper was designed round an 80mm fork and the headtube is very short.

put an emergency 26" in my 29" wheel, felt awful, very squirmy around corners, thought the tyre was going to roll off the rim, ok for "slowly get you home" emergencies

p.s. agree 120mm is too long Clubber

Yeah agree too. I was working on the basis that they could be shortened to 100mm

To calculate trail:

h = headtube angle
f = Fork offset
r = radius of tyre
t = trail

then t= (rcosh - f)/sinh

To reiterate what I said in the email (before its to late 😉 )
I ran the viper on a 440AC RC31, & TBH I thought it was trying to kill me!
Now I'll admit I'm only 6', but I now run exactly the same stuff on an OO scandal, albeit with a longer stem, & it feels quick steering but not nervous, now just so you know its not me being a woos, I let a roadie friend have a go & he thought it was stupidly steep/'quick steering'.

So,
1, you know its long in the TT

2, you know the steering will be silly on short AC forks

3, you know the paint is crap 😉

4, you know your only sending me money for postage, you have it on approval.

Cheers.

hmmm I'd just get a Swift. Yes they look expensive, but are wrth it IMO

Are you going to give me the money I don't have for it? 😉

You wouldn't want one anyway as they are blue and not some silly purple colour 😉

I recommend a Swift because your 853 SS is a pretty good bike (I swapped from an 853SS to a swift) and a Swift will give you the same kind of ride quality. Its just a really sorted bike. I'd be saving up the extra pennies!

It's a fair point but I quite like the Singular blue as it happens 😉

As I said on the day clubber, you looked 'right' with a 29er, hopefully it will ride as well.

I have to say my 29er felt a little sluggish steering wise.

This made perfect sense to me in that the wheels have 10% more weight 10% further away from the timr.

cynic-al I would not disagree with that. There are some distinct compensations though. Mainly that lovely blue colour hmmmmmm 😀

I already have a bike in a pretty similar blue (the 26" one I was riding at BBF 🙂 )

Ah, so you have started to convert over. Good. Well there you are then. Sell that purple thing, get a Swift and your bikes will match. Always important to have a matching "quiver". 8)

http://www.dirtrider.com/tech/141_0908_tech_tips_motorcycle_rake_and_trail/index.html

I wonder whether clubber can drag this out to 100 posts, 6 months later and still no 29er?

Get 10% lighter wheels and anticipate a bit more - that more than compensates for perceived slowness!

I'll give it a go 😉

Actually I should have the frame on the way shortly, I already have the wheels so just need to find a set of suspension forks..

TooTall - Member

Get 10% lighter wheels and anticipate a bit more - that more than compensates for perceived slowness!

You know what - I did (the latter)! But thanks for the helpful (and not at all pompous) advice!

I wasn't seeing it as a negative - it suited the bike tbh, but it was always noticeable as I was swapping with 26ers. I sold the 29er in the end, couldn't justify it albeit there were interesting facets.

I read the advice as "spend more and ride better" - Practical advice we should all aim for 😉

That Tony Foale article is really very interesting. In that his experiments keep trail constant, while altering head angle and rake/offset. His conclusions are somewhat surprising though, that a steep head angle (what we would call 90deg) and negative offset to achieve a certain trail figure provide improved handling over a more traditional ~75deg head angle. The determination that 'ideal' trail is related to wheel size also accordsd with my experience. How you go about achieving that trail figure (slack head angle and lots of offset, or steep and little offset) also has a significant impact on how the bike rides. Would be interesting to repeat similar trials on a bicycle. I've done it to a degree, but only within what would be accepted as relatively 'normal' in a bike environment.

clubber have just e-mailed you.

Get 10% lighter wheels and anticipate a bit more - that more than compensates for perceived slowness!

yep, i'm currently running an alfine and halo freedom rims/halo tyres on my swift - 28plus pounds which is hefty and has made me pay a lot more attention to my bars/stem/saddle postion to eek out the best handling and i'm saving for some lighter wheels!

Sam - Member
That Tony Foale article is really very interesting

It works on motorbikes for sure. In about 1972 my brother & I were riding long distances in the bush in Oz and basically we had to go fast to get anywhere (like Mt Isa to Birdsville for a weekend).

He had a Suzuki 500T. After a bit of experimentaion we lengthened the swing arm and jacked up the rear suspension for more travel (which steepened the head angle), then reversed the fork yoke to pull the front wheel back and get more trail. It could be held flat out on the dirt and wasn't troubled by deep holes full of bulldust whereas I ended up doing cartwheels at 90mph just south of Bedourie trying to keep up with him, and ended up somewhat bent and battered.

Phil Irving explained it best IMO

I mostly take the proverbial given that I just ride bikes cos I likes it - I could care less about stuff because my bikes work for me and thats about all that matters. I do like al being a mardy old man tho - that pleases me.

It entertains me too 🙂

Go for the swift and stop worrying about all those things as there already done for you 😀

riding long distances in the bush in Oz and basically we had to go fast to get anywhere (like Mt Isa to Birdsville for a weekend

That is a bloody long way - what like nearly 1000k each way for the weekend? On dirt roads? There must have been something pretty special in Birdsville in those days!
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Beer 🙂

The place looks much tidier in that pic, and is that a bitumen road now?

The other weekend destination was Townsville to stare at the sea and scantily clad women from the Seaview Hotel. Leave from work at 5pm Friday and aim to arrive back at work for 8am on Monday. It was an easier ride, about 900km each way and only half of it dirt.

Sam, since you're on...

Does the £420 for the Swift include the fork? Do you sell them without (as I'd like suspension) and if so, how much?

Actually, ignore me. Bl00dy STW. I haven't got the cash for it and I'm sure that the Viper is more than capable for starters 🙄

This is a cool article from the old days re bicycle stability:

[url= http://www.phys.lsu.edu/faculty/gonzalez/Teaching/Phys7221/vol59no9p51_56.pdf ]Clicky Click[/url]

bit in depth but interesting

Clubber, yes, the price includes the fork. If you don't need one I can certainly do a bit better. In fact as I have a bit of an excess of XL frames at present, and some old stock, I could perhaps do even better. Drop me a line and perhaps we can work something out. The Viper isn't a bargain if you end up replacing it in 6 months time 😉

Of course there is also [url= http://www.flickr.com/photos/singularcycles/sets/72157623949749566/ ]this[/url] cluttering up the shed...

A month ago I swapped out the RRalf on my front wheel to try a Bonty XDX and was almost caught out by its fast responsiveness.

Sam = bad man

😀

If only those XL were a man's XL.

If only those XL were a man's XL.

They are pretty big - 25.3" ett - longer than the longest Fisher for instance. If you really need bigger I can do it (in Ti) as well. I reckon they suit guys (and girls potentially) up to about 6'6", it just doesn't make sense for me to make production frames any bigger than that.

TooTall - Member
I mostly take the proverbial given that I just ride bikes cos I likes it - I could care less about stuff because my bikes work for me and thats about all that matters. I do like al being a mardy old man tho - that pleases me.

Sam YGM

http://www.63xc.com/willm/rmint.htm

shrink that pegasus to L please!

Have a squint at this (great 29er site an all)
http://twentynineinches.com/2010/02/16/its-all-about-trail-a-look-at-recent-changes-in-29er-geometry/

Clubber - The Swift is a fantastic bike and will knock spots off the Viper. I know its steel not alloy and a more expensive frame but if you can strech to one then do 😉

Sam - I might be in touch soon about that crash replacement if you have some XL's kicking around 😕

What have you done bigsi?

So RD - did you find the Swift too slack with the 120mm Manitous?

um...not sure if i'd say slack, just felt too tall at the front somehow, definately not as good as the rigids feel ride height wise

Swift does ride lovely rigid eh RD?

it does, but my biceps and forearms now look like popeyes from riding the last few weeks over the concrete like trails with built in hoofprints from the winter

I did find the rigid on Barney's Swift to be particularly good as far as rigids go (and it's amazing just how much you could see it flexing compared to say the rigid exotics I have on my 26" SS) but it's still a rigid fork and I definitely want suspension on mine as I have nothing to prove 😉

Yes there it that 😆 Still makes a satisfying change from bouncy bikes. What tyres do you use? I want to go BIG on the front of mine 😀 Oh and a carbon bar helps a bit.

Maybe Sam would like to expound on the art of riding rigid. He's pretty good at it, and the Swift is comfortable as a rigid compared to other bikes.

I often think people who are used to riding with suspension are trying to ride with a death grip when they get on a rigid.

Bonty XR on the front of mine crossmark on the rear

Agree about the deathgrip 🙂

I still ride rigid through the winter and in fact started out mtbing rigid back in the day but I just find that trails (at least the ones I ride) flow better with a suspension fork to take out some of the chatter from the front. I don't think that the deathgrip thing is the issue for me at least - certainly I can ride a CX bike with tyres at 85psi pretty quick over bumpy ground 😉

Like I said, I did find the Swift particularly good for rigid but it's still not suspension.