HTA, how steep is too steep....

[pale scotsman]

for a recreational rider? This may be a stupid question, but the reason I'm asking is that I've ridden from a 72 to a 73.5 degree head tube angle on various frames and they all feel "OK" to me.

Is a 74 pushing it for hands off the bars, at times, cruising around? I'm not going to race, just ride for fitness. For reference I'm talking about 60 ctc frames with a 59ish top tube.

Thanks!

[Smiley]

Pale Man , Last week we did the BBC century and rode by the Mount . Anyway I think you need to look at rake along with HTA ? Its the trail number that important to me , Serotta will work around a 5.8 number and my next bike will be around 5.9 - 6.0 cause I want the thing to track a very steady line at high speed, like my tandem .

[Tom Robison]

Mr. Smiles, I am getting a new Legend. Using the trails xls. file found on the Anvil Bike website, the trail on my new bike will be 6.02. Can you explain a bit about trail? Is there a point trail can be too high?

http://www.anvilbikes.com/story.php?module=calculators

Tom

[Smiley]

I really think its up to the designer of the frame to dial in the trail to make the front handling what you want to feel in the front handling of the bike. I bet my tandem trail is BIG , certainly larger than my Hors , Now I have screwed up my Hors trail a bit when I switched the fork to a higher spanned fork from my F1 , I think I am now 372 mm versus the F1 at 365 mm so I raised my front end a bit , like making my head angle slacker ( I think ) . Anyway I knew this modifcation would effect my trail and had discussed it with the know it alls at Reynolds and Alpha and nobody including Master Builder Kelly Bedford could give me a diffinative answer on what was going to happen to my steering. Anyway not to bore you but if you do a search on my posts you'll find a long history on Trail and subsequent discussions as I has swapped my trusty BUT heavy F1 for an Ouzo Pro and lots came out of these threads.
The answer to your question on trail and I know Dave Kirk has answered it best , there is a relationship between head angle and rake that determines trail . Think of casters on a grocery cart as best put by Kirk , without the off-set of the wheels ( trail ) the wheels would not track staright .

[cpg]

Pale Scotsman,

As usual others have posted some fairly well reasoned posts but regarding 74 degree HTA's, I think 74 is getting a little too steep for they type of riding that you've described. I say this regardless of the fork offset and resultant trail numbers. IMHO steep head angles feel "fast" and "fun" for short test rides but over the long haul they become annoying. Sort of like ultra short wheelbases. It feels good for a while but that constant attention needed to keep the bike from "snaking" down the road can become tiresome.

[pale scotsman]

Thanks for the replies guys. I've never fully grasped trail so I better to a little studyin' up.

Sir Smiley, I'll bet the Mount was beautiful this time of year. I used to ride up and down the hill to the grotto, and routinely "smoke" the brake pads on the way down. Steeeeeep hill.

[Ray]

Pale Scotsman,

As usual others have posted some fairly well reasoned posts but regarding 74 degree HTA's, I think 74 is getting a little too steep for they type of riding that you've described. I say this regardless of the fork offset and resultant trail numbers. IMHO steep head angles feel "fast" and "fun" for short test rides but over the long haul they become annoying. Sort of like ultra short wheelbases. It feels good for a while but that constant attention needed to keep the bike from "snaking" down the road can become tiresome.

I tend to be a pretty relaxed rec rider without too many aggressive bones in my body. My favorite ride is a Rivendell Road with reasonably relaxed angles and a long wheelbase. I can't stand really quick steering bikes for any distance at all. About a year ago I bought an old ('92) Bridgestone RB-1 that has a 74 degree HTA. While the steering is quicker than any of my other bikes (it's the only true racing geometry bike in my stable), it's far more stable and planted under me than other race bikes I've had with 73 and 73.5 degree HTAs. So I agree with the others that you have to look at the whole package, rake, trail, rear center/front center relationship, etc.

-Ray

[Needs Help]

I've never fully grasped trail so I better to a little studyin' up.

This would be a start:

http://www.phred.org/~josh/bike/trail.html

[cpg]

I tend to be a pretty relaxed rec rider without too many aggressive bones in my body. My favorite ride is a Rivendell Road with reasonably relaxed angles and a long wheelbase. I can't stand really quick steering bikes for any distance at all. About a year ago I bought an old ('92) Bridgestone RB-1 that has a 74 degree HTA. While the steering is quicker than any of my other bikes (it's the only true racing geometry bike in my stable), it's far more stable and planted under me than other race bikes I've had with 73 and 73.5 degree HTAs. So I agree with the others that you have to look at the whole package, rake, trail, rear center/front center relationship, etc.

-Ray

Agreed, the whole package is important BUT given the only datum given was a 74 degree HTA there wasn't much more of a package. Are you sure that the head angle is 74 on your RB-1? Every one of those that I've repaired had head angles of 73 degrees.

[Ray]

Agreed, the whole package is important BUT given the only datum given was a 74 degree HTA there wasn't much more of a package. Are you sure that the head angle is 74 on your RB-1? Every one of those that I've repaired had head angles of 73 degrees.

... the '92 RB-1 had a 74 degree hta on the 59cm frame. The two sizes below that are 73.5 and the smaller ones are 73. With all of the high zoot stuff out there that I've tried and liked but not liked that much, I'm constantly amazed at how much I love the feel of that old frame.

-Ray

[BigMac]

A lot depends upon usage and frame size. As Smiley noted, Serotta builds to a 58mm trail, although I doubt this is across the board in all frame sizes. As frame sizes grow, so do front-center and wheelbase which helps tracking and stability. A large frame can feel sluggish and unresponsive on turn initiation with a too short of trail. Many builders define a "nuetral" front end as 57.5mm trail but will design smaller frames with less trail. Lower trail frames take a bit more attention and/or effort to lean the bike into turn. The shorter wheelbase however makes turning easier and the shorter trail frame will feel more stable. Too much trail will dive into turns inconsistently and feel too quick. At higher speeds however the longer trail bike feels more stable and responsive.

That said, its not just trail that defines stability, turn-in response, etc. The tandem you mention Smiley, tracks like its on rails because well... its wheelbase is massive as is its turning radius. Its trail however may in fact be quite short due to the long rake fork. I recall most tandem forks in the 55mm rake range, no? I think you will find it tough to keep trail above 55mm with that much rake using "normal" head angle -- 71-72* for tandems, no? For the example of the 74* HTa single, you may need to find a very short rake fork for proper response..and honestly even that is a serious compromise. Take a 74Hta frame with a 37.5mm rake fork and compare the ride/response with a 73HTa frame equipped w/44mm rake fork, same materials, wheels etc. These 2 bikes would have very similar trail (+/- .5mm if memory serves) yet would feel and respond quite differently, the 73/44 feeling more stable at speed, easy to ride hands-free, etc.

A great example of this is to look at vintage Faleiro Masi frames which heavily influenced the later Ugo DeRosa and Eddie Merckx frames. These frames typically offered 72.5-73 HTa but very lengthy 5cm raked forks. Result is relatively short trail but also frames noted for their stability. They do in fact take perhaps a bit more effort for turn in but are less suceptable to bump-steer over the European cobbles. Now I admit to being biased because well, I spent my 1st 20 years of serious cycling on Masi's, DeRosa and Merckx but I would personally avoid ANY frame w/74HTa. I favor going shallower on the HT, longer fork rake, longer chainstays. Then again, my riding primarily consists of climbing and descending on steep roads in poor condition. If you are riding smoothly paved tarmac and flatter terrain, your experience and favor may differ. FWIW: my Legend is 73Hta, equipped w/43mm rake F1 fork, it is a model for smooth and stable descending, hands free at 40mph w/o worry.

Ride on!

[Smiley]

Thank you Big Mac and good to see you again , since you last visited with us apre's your sons baseball tourney ( how'd he do anyway ) in Tulsa , I have been back to Tulsa twice more than I would have dreamed of .
I do agree that trail by itself or HTA are not good indicators . Kelly Bedford and I discuss front end handling for all my bike fits especially if I have a client that rides a bit more up-right ( higher center of gravity ) or as we would say does not have the front wheel weighted , I would tend to go longer on the trail and Kelly does his additional thing to make sure we have a stable front end cause the client aint going to decend with his weight down low. My next bike will favor a bit more trail then what I have been using. I'll check my tandems HTA from Co-Mo's web site cause that suckers is really a sweet decending machine and I find that the front end is not as slow as a Santana thru the turns .

[zap]

Interesting subject.

Most certainly the entire package. One of my more stable bikes has a 5.6 (or 5.4 according to Anvil spreadsheet) )trail with a 4.6 rake and 73 HA. Wheelbase is 100.5.

My quicker handling bike has 6.0 trail with 3.5 rake and 73.9 HA. Wheelbase is 100.5.

So this would confirm some of what Big Mac posted.

But, one also needs to factor front ctr., stem length and set back into the equation. This will determine how the weight is distributed as well. Wouldn't weight distribution affect handling as well?

Our CoMo tandem has 5.6 trail with 3.8 rake and 74 HA. Wheelbase, well longer than any single :rolleyes: