Covet

[GB]

@hozn 114435 wrote:

Maybe. I can definitely feel the difference in steering my road vs my cx bike; that is 1° difference (73.5 vs. 72.5). The rake is slightly different, though (43mm vs 45mm). And I can definitely feel the handling difference between my cx bike and slacker MTB (71°, 45mm rake). The 1° is not huge, but I think you would feel the bike behaving differently if you were able to hold all other things constant.

Ok, I think I see what’s going on. They change the HTA with the bike size. My 54 bike needs a shallower HTA than your 57(?) to give the same level of responsiveness. From my research on 54 size bikes 73 road, 72 CX and 71 MTB are reasonable HTA +/- 0.5 degrees.

[hozn]

I think the geometry changes are about accommodating what “fits” around the wheels. I think the forks are all the same regardless of size, so I would expect the handling to be different as the HTA changes. (Yeah, my bikes are 59, 60cm.)

But yeah, 71, 72, 73 are reasonable mtb, cx, road angles. In my experience these handle noticeably differently when it comes to trading low-speed stability for high-speed agility.

[GB]

@hozn 114437 wrote:

I think the geometry changes are about accommodating what “fits” around the wheels. I think the forks are all the same regardless of size, so I would expect the handling to be different as the HTA changes. (Yeah, my bikes are 59, 60cm.)

But yeah, 71, 72, 73 are reasonable mtb, cx, road angles. In my experience these handle noticeably differently when it comes to trading low-speed stability for high-speed agility.

Glad we are generally in agreement on HTAs, and I agree the forks are the same. And I guess with this I’ll say that 1 degree does make a difference, but… HTAs change with size and rake is also a factor.

Regarding changing the HTA with the bike size, the lower angles of the smaller bikes would ‘fit’ on bigger bikes. But since they are not needed to accommodate the wheels and because they result in a longer wheel base and therefore a less responsive bike the angle is increased. I think this is doconclusion the bikes performance more uniform across sizes.

In conclusion talking about HTA w/out size doesn’t convey much information and I still haven’t been talked out of the size 53 frame with a 71.5 HTA. Edit: double checked and its 70.5 sooo maybe I have been talked out of it. #thesearchcontinues

[jabberwocky]

71 is awful steep for a modern MTB. Even more racy XC oriented bikes are usually under 70 these days.

[TwoWheelsDC]

@hozn 114435 wrote:

Maybe. I can definitely feel the difference in steering my road vs my cx bike; that is 1° difference (73.5 vs. 72.5). The rake is slightly different, though (43mm vs 45mm). And I can definitely feel the handling difference between my cx bike and slacker MTB (71°, 45mm rake). The 1° is not huge, but I think you would feel the bike behaving differently if you were able to hold all other things constant.

You should ride my MASH…HTA is 75 with 28mm rake!

[hozn]

@jabberwocky 114444 wrote:

71 is awful steep for a modern MTB. Even more racy XC oriented bikes are usually under 70 these days.

That may be true; I’m talking about my Jabberwocky, but my Voodoo before that had a 72º HTA and GT Avalanche had a 70.5. My full suspension DB Sorite did have a 69.5º HTA; that definitely felt quite different too (though obviously a lot of differences going on there).

@TwoWheelsDC 114447 wrote:

You should ride my MASH…HTA is 75 with 28mm rake!

I assume that’s track-bike geometry? It would make sense that they’d not need slow-speed handling, though I don’t have any idea how the very short rake (short rake = more stability, long rake = twitchier) would offset the steep HTA. I’m sure one could draw it out and see how those interact to determine the effective steering point / speed.

[hozn]

@GB 114442 wrote:

Glad we are generally in agreement on HTAs, and I agree the forks are the same. And I guess with this I’ll say that 1 degree does make a difference, but… HTAs change with size and rake is also a factor.

Regarding changing the HTA with the bike size, the lower angles of the smaller bikes would ‘fit’ on bigger bikes. But since they are not needed to accommodate the wheels and because they result in a longer wheel base and therefore a less responsive bike the angle is increased. I think this is doconclusion the bikes performance more uniform across sizes.

In conclusion talking about HTA w/out size doesn’t convey much information and I still haven’t been talked out of the size 53 frame with a 71.5 HTA. Edit: double checked and its 70.5 sooo maybe I have been talked out of it. #thesearchcontinues

Yeah, I think we agree Fork rake is certainly an important component. While the 45mm rake is pretty typical for CX, I see that the Renegade specifically specs a 50mm-rake fork, so that probably offsets the slacker HTA to make a more responsive bike?

Really, one needs to use a trail calculator — like this one http://yojimg.net/bike/web_tools/trailcalc.php — since trail is, I believe, what is being perceived here.

So here are a few trail comparisons:
Jamis Renegade: HTA=71.5, Rake=50mm. Trail w/ 32mm tires = 60mm, Trail w/ 25mm tires = 58mm
Vassago Jabberwocky 29r: HTA=71, Rake=45mm. Trail w/ 2.3″ tires = 76mm
my Habanero CX bike: HTA=72.5, Rake=45mm, Trail w/ 42mm tires = 62mm, Trail w/ 25mm tires = 57mm
my road bike: HTA=73.5, Rake=43mm, Trail w/ 25mm tires = 54mm
TwoWheel’s MASH: HTA=75, Rake=28, Trail w/ 23mm tires = 59mm

So that’s interesting. I’d like to understand better how slackening the head tube and increasing the rake (aka offset) affects the handling, even it trail remains constant. There is some suggestion from the MTB marketing that this makes a good “best of both worlds” bike (responsive enough at slow speed but also tracks the line nicely at higher speed), but I don’t know what that would mean.

One thing that was less obvious to me before this exercise was the huge affect that tire size has on these numbers. E.g. the 2.3″ tires on the Vassago make a big difference in the trail (compared to, e.g., putting road tires on that bike which would drop the trail down to 66m). Obviously suspension forks throw a wrench in things too since the trail won’t be constant.

To the point about frame sizes and geometries changing, that is definitely true. I read somewhere that most frames are optimized around the 56cm size, since that is the most popular. Makes sense. Not sure how these geometry changes might result in different feels on the different sized frames.

[jabberwocky]

@hozn 114453 wrote:

That may be true; I’m talking about my Jabberwocky, but my Voodoo before that had a 72º HTA and GT Avalanche had a 70.5. My full suspension DB Sorite did have a 69.5º HTA; that definitely felt quite different too (though obviously a lot of differences going on there).

My main trail bike (Ibis Mojo HD) is about a 66º head angle. Its definitely a handful on tight, twisty trail and takes a bit of work to keep the front end down on steep climbs, but it more than makes up for it everywhere else.

[GB]

@jabberwocky 114457 wrote:

My main trail bike (Ibis Mojo HD) is about a 66º head angle. Its definitely a handful on tight, twisty trail and takes a bit of work to keep the front end down on steep climbs, but it more than makes up for it everywhere else.

Wahoo, I can keep coveting that 53cm frame with the 70.5 degree HTA and a standard 45mm rake. (Which is how this discussion relates to the thread). Now I need to find a shop carrying a similar bike so I can test ride.

With additional in put and more research, I’ll update the MTB, CX, and road HTA for a 54 frame to give a a wider spread between each; 69, 71, 73.

[hozn]

@GB 114468 wrote:

Wahoo, I can keep coveting that 53cm frame with the 70.5 degree HTA and a standard 45mm rake. (Which is how this discussion relates to the thread). Now I need to find a shop carrying a similar bike so I can test ride.

With additional in put and more research, I’ll update the MTB, CX, and road HTA for a 54 frame to give a a wider spread between each; 69, 71, 73.

Well, since you like to ride without hands [on your bars], you probably do want to keep your steering slow / long-trail

But I would expect the steering on that hypothetical frame (calculator says 72mm trail for 35mm tires, 68mm for 25mm tires) to feel pretty slow. (Of course, probably great for singletrack, less ideal if you want it to be a ride-fast bike too?) Granted that it will still be a lot quicker turning than the trail-bike Ibis Mojo HD

[vvill]

belt drive, disc brakes, thru axles:

[KayakCyndi]

@vvill 114471 wrote:

belt drive, disc brakes, thru axles:

Funny, Matt and I were just discussing that bike this morning …..

[Powerful Pete]

Hadn’t thought about belt drives… Rohloff… mumble…

[DaveK]

@KayakCyndi 114477 wrote:

Funny, Matt and I were just discussing that bike this morning …..

My brother and I were talking about that bike last night.

Be right back, taking a casual trip by Bikenetic…

[vvill]

@DaveK 114487 wrote:

Be right back, taking a casual trip by Bikenetic…

I mentioned the existing season’s model of this bike to Jan once. He asked me my size, and I quickly had to back down to avoid the possibility of having a “test model” ordered.

[Author]

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