Stem Length Steering Geometry
Stem Length Steering Geometry
My 2006 Dawes Ultra Galaxy steering feels twitchy. Could it be my balance? Would a shorter stem make things better or worse?
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reohn2
I don't think you could describe a Galaxy's steering as 'twitchy',stable,predictable,safe,yes but not twitchy.
I don't think the length of stem will make any difference,it seems to be a bit of a myth that the longer the stem the more twitchy the steering.
Have you checked the headset bearing adjustment/lubrication/wear,or front wheel bearings,adjustment/lube etc ,or front wheel rim truth,front tyre ,condition/pressure etc?
I don't think the length of stem will make any difference,it seems to be a bit of a myth that the longer the stem the more twitchy the steering.
Have you checked the headset bearing adjustment/lubrication/wear,or front wheel bearings,adjustment/lube etc ,or front wheel rim truth,front tyre ,condition/pressure etc?
,it seems to be a bit of a myth that the longer the stem the more twitchy the steering.
It's the other way around, the shorter the stem the twitchier it may be. Only because a shorter stem moves your hands nearer the steerer so you have to move your hands less to turn the front wheel a given amount. Same with the width of handlebars. However, for deliquium changing the stem may not work because the length needed to have any noticable impact might also be so long that riding becomes very uncomfortable and stretched.
deliquium, are you sure that the bike is the right size for you?
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reohn2
deliquium
Have you changed the tyres recently or done anything else which coinsides with the twitchiness?
The reason I ask is that one of my bikes(not a Galaxy)doesn't like a certain make of tyre (doesn't become twitchy just changes its charechteristics(sp?).
Si
I can't agree with you about twitchiness and stem length.
Have you changed the tyres recently or done anything else which coinsides with the twitchiness?
The reason I ask is that one of my bikes(not a Galaxy)doesn't like a certain make of tyre (doesn't become twitchy just changes its charechteristics(sp?).
Si
I can't agree with you about twitchiness and stem length.
the current trend is to have a smaller frame with more seatpin sticking out. Fine, in my opinion it looks better and saves weight. However, most off the peg frame manufacturers haven't allowed for this - they sell a shortened seat tube by speccing a smaller frame which has too short a top tube, which then makes the bike feel twitchy. So for example, I traditionally ride a 22in seat tube and 22 in top tube. If I want to look "modern" with more seatpin sticking out, then I buy say a 21 in frame. But the top tube is then also 21in and it all feels twitchy. Hence the reason my latest frame is custom build and my previous frame was sold, as this also felt twitchy and didn't flow round corners. You might also have read that some pros specifiy long length top tubes - I guess its for this very reason.
Perhaps your galaxy is one size too small (short), cos galaxies are renowned for their durability and stability. I also think that the different ways of measuring compact frames and the SML sizing doesn't help consumers make the appropriate choice.
Perhaps your galaxy is one size too small (short), cos galaxies are renowned for their durability and stability. I also think that the different ways of measuring compact frames and the SML sizing doesn't help consumers make the appropriate choice.
Bikes feel twitchy when they don't have enough self-steering torque helping to keep the front wheel pointed where it's going. This torque or caster action, call it what you will, is the product of trail and front tyre rolling drag.
Touring bikes, in fact, commonly have less trail than racing bikes. That's because they are assumed to have softer tyres with more rolling drag, in which case you don't want as much trail or else the steering would be too stable. More weight on the front tyre also increases its drag, so bikes designed for front luggage may have even less trail.
And there's another factor: the need for toe clearance often prompts bike builders to increase the fork rake (offset) of touring bikes beyond what is optimum for the head angle (rather than slacken the angle itself), thereby further reducing the trail.
So paradoxically, it is not at all unusual for touring bikes to feel twitchy, particularly when fitted with smoother, harder tyres than usual and ridden without any front luggage.
French cyclotouristes traditionally carried most if not all of their luggage in front panniers. That's partly because they rode bikes with racing style, 73 degree or even steeper head angles and shortish top tubes, which then needed generous fork rake to provide toe clearance for mudguards (not to mention comfort). The combination of a steep head angle and long fork rake results in very little trail. Ridden unladen or with rear luggage, those bikes had very light steering and often exhibited shimmy.
The reason bikes with longer stems feel more stable is that the associated riding position brings a greater percentage of bodyweight onto the front wheel, increasing its drag and self-steering torque (reducing rear tyre drag by the same amount of course). But to change stem length on account of this is to put the cart before the horse. You need whatever stem length provides the optimum position for your build and style of riding.
Touring bikes, in fact, commonly have less trail than racing bikes. That's because they are assumed to have softer tyres with more rolling drag, in which case you don't want as much trail or else the steering would be too stable. More weight on the front tyre also increases its drag, so bikes designed for front luggage may have even less trail.
And there's another factor: the need for toe clearance often prompts bike builders to increase the fork rake (offset) of touring bikes beyond what is optimum for the head angle (rather than slacken the angle itself), thereby further reducing the trail.
So paradoxically, it is not at all unusual for touring bikes to feel twitchy, particularly when fitted with smoother, harder tyres than usual and ridden without any front luggage.
French cyclotouristes traditionally carried most if not all of their luggage in front panniers. That's partly because they rode bikes with racing style, 73 degree or even steeper head angles and shortish top tubes, which then needed generous fork rake to provide toe clearance for mudguards (not to mention comfort). The combination of a steep head angle and long fork rake results in very little trail. Ridden unladen or with rear luggage, those bikes had very light steering and often exhibited shimmy.
The reason bikes with longer stems feel more stable is that the associated riding position brings a greater percentage of bodyweight onto the front wheel, increasing its drag and self-steering torque (reducing rear tyre drag by the same amount of course). But to change stem length on account of this is to put the cart before the horse. You need whatever stem length provides the optimum position for your build and style of riding.
Chris Juden
One lady owner, never raced or jumped.
One lady owner, never raced or jumped.
The Galaxy is definitely the correct size, being almost identical in terms of top tube length, as my old Longstaff. And one would expect it to be a "lazy" steerer, as it is a touring bike. Tyres are standard Marathons. I am riding with the handlebars some 30mm higher than in the past - now just a tad below saddle height.
What is the correct relation to stem lenght and twitchiness? Some confusion here?
I forgot to mention, I have had a 5 year sabbatical from bikes. Although have now done over 1500 miles on the Galaxy. Makes me think it might be me and not the bike? Am only 53 and don't wobble off the bike!
What is the correct relation to stem lenght and twitchiness? Some confusion here?
I forgot to mention, I have had a 5 year sabbatical from bikes. Although have now done over 1500 miles on the Galaxy. Makes me think it might be me and not the bike? Am only 53 and don't wobble off the bike!
Thanks Chris,
I will try, as an experiment, to lower handlebars - and thereby increase weight on front wheel - to see if that does make a difference. If it does - my quest for a more comfortable and upright riding position will be compromised though.
Haven't been riding with more that two bottles of wine in the small rear panniers - so not over laden on the back end!
I will try, as an experiment, to lower handlebars - and thereby increase weight on front wheel - to see if that does make a difference. If it does - my quest for a more comfortable and upright riding position will be compromised though.
Haven't been riding with more that two bottles of wine in the small rear panniers - so not over laden on the back end!
Have lowered the handlebars to 30mm below saddle height. Just back from a hilly 30 miles - unavoidable living in Snowdonia - and it still feels twitchy, especially going down the long Llanberis Pass, as well as on the flat.
Tyres are standard 32mm Marathons.
Anyone else got a newish oval downtube Galaxy with a similar problem?
Anyone else found their own internal balance deteriorate?
Tyres are standard 32mm Marathons.
Anyone else got a newish oval downtube Galaxy with a similar problem?
Anyone else found their own internal balance deteriorate?
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reohn2
deliquium wrote:Front tyre pressure = 5 Bar - 72 PSI - ride feels comfy, as opposed to hard.
Nothing wrong there then,if everything else checks out OK, I'm stumped
.
Perhaps a trip to the LBS to have the bike checked over or let a friend take it for a ride see what they think.
PS we were riding for a short while recently with a rider whose bike appeared very twitchy but the rest of the group thought it was the rider and not the bike, though its impossible to say unless one rides the bike ones self.
Couple of points :
1. just thinking back many years. Once out on a clubrun a mates bike felt twitchy, but we couldn't explain why. It was a bike he had used before with no twitchiness and was a fairly new frame. A few miles on and something began to seperate on the forks (steel ones). Can't quite remember what - steerer to crown, or blade to crown or something. Thing is he managed to ride home steadily on it. might be worth checking all welds etc are ok.
2. I remember building up a mountain bike with kids seat on the rear to carry baby. I also used the same bike for commuting to work. If I rode the bike with an empty seat, then all was ok. When I rode to work with a small, lightweight rucksack in the baby seat, the bike was twitchy and shimmied and felt unsafe. When I had baby on board, steering felt ok again. Can't explain it.
1. just thinking back many years. Once out on a clubrun a mates bike felt twitchy, but we couldn't explain why. It was a bike he had used before with no twitchiness and was a fairly new frame. A few miles on and something began to seperate on the forks (steel ones). Can't quite remember what - steerer to crown, or blade to crown or something. Thing is he managed to ride home steadily on it. might be worth checking all welds etc are ok.
2. I remember building up a mountain bike with kids seat on the rear to carry baby. I also used the same bike for commuting to work. If I rode the bike with an empty seat, then all was ok. When I rode to work with a small, lightweight rucksack in the baby seat, the bike was twitchy and shimmied and felt unsafe. When I had baby on board, steering felt ok again. Can't explain it.