BMC - why the long trail?

[pff]

I have a BMC roadmachine and in terms of chainstay length and front-center it's pretty much halfway in between both my racing-geo bike (a cervelo) and my gravel bike. The stack/reach on all 3 are essentially identical.

I like a lot of stuff about the BMC but I've never liked the way it carves turns, or fails to. I have to start turning much earlier and it never wants to hold its line --- very easy to oversteer (due to high wheel flop?).

Both the gravel bike (when running road tires) and the racy bike handle subjectively "better" on descents. The racy geometry in particular goes where I want it to on a moment's notice. But even the gravel bike which seems similar in a lot of measurements is more confident in descending.

I've attempted to understand where this subjective feeling comes from. This has led me to reading about trail, rake and flop. It appears that not just the endurance BMC but all BMC road bikes (team machine SLR, new team machine R, road machine...) have outlandishly high trail and therefore flop. The BMC site lists trail at 63mm but by my calculations they are using a 25mm tire for this figure, whereas most of us are using closer to 30mm these days which puts trail at 65mm.

BMC seems pretty far from the industry standard in this regard but I've never heard this mentioned by any bike reviewers or other blokes on BMCs. What gives?

3 bikes in question for reference

[Clean39T]

Yeah, my Teammachine SLR01 Disc in 61cm has 64mm trail w a 28mm tire --- and I love it.. no toe overlap, steady and calm in sidewinds and downhills, and zero handling negatives on the rough streets I ride. I do notice the flop on 20% grades out of the saddle but I got used to it after a ride or two -- and the positives vastly outweigh the negatives for me.

[Dadoflam]

Cadel Evans was retained by BMC on staff after he stopped racing to developand refine the geometry and handling of the road frames.
In no small part this was because was one of the very technical riders with an intimate knowledge and understanding of his bikes and geometry requirements.
What you are riding is the outcome of this input.

[Dadoflam]

Cadel Evans was retained by BMC on staff after he stopped racing to develop and refine the geometry and handling of the road frames.
In no small part this was because was one of the very technical riders with an intimate knowledge and understanding of his bikes and geometry requirements.
What you are riding is the outcome of this
Your observations are interesting as the handling of BMC’s products are frequently reviewed as one of their strengths - especially the Team Machines.

[Peter P.]

You mean to tell me your Parlee, with the same head angle as the BMC but a mere 2mm more fork rake, handles much better? I can't believe 2mm makes that much of a difference. It's the tire size I tell ya!

I've experimented with rake and trail on my bikes and will say yes; 5mm makes a easily discernable difference. 2mm, no.

I'd temporarily put 25s on the BMC and confirm it handles better. Then either buy another fork or get rid of the bike. I think part of your problem is the gyroscopic effect of the heavier, larger tire and tube.

Oddly enough, retired framebuilder Dave Moulton who had quite a following in the 80s and 90s, built high trail road frames and people liked them! I was always intrigued by his bikes and wanted to try that geometry.

My road bike with 25s has a 72 degree/50mm front end so my impressions somewhat relate to the numbers you provided.

Edit: I didn't see which size tire you spec'd on the BMC and got it and your gravel bike confused. If you're running 25s on the BMC and it rides like crap, then Cadel Evans and you have different tastes in bikes.

Originally Posted by Clean39T

... steady and calm in sidewinds and downhills, and zero handling negatives on the rough streets I ride. I do notice the flop on 20% grades out of the saddle but I got used to it after a ride or two..

I'll confirm Clean39T's observations. My 72/50 mentioned above was spec'd by me on my road bike. I wanted a bike which would get tossed around less in those blustery spring winds and this combination worked. Also like Clean, I do experience a very small wheel flop at slow speeds say, under 7mph and going up hills, particularly noticeable standing out of the saddle. Hardly a deal breaker and certainly not a compromise in performance.

[Pastashop]

Originally Posted by Peter P.

You mean to tell me your Parlee, with the same head angle as the BMC but a mere 2mm more fork rake, handles much better? I can't believe 2mm makes that much of a difference. It's the tire size I tell ya!

I've experimented with rake and trail on my bikes and will say yes; 5mm makes a easily discernable difference. 2mm, no.

I'd temporarily put 25s on the BMC and confirm it handles better. Then either buy another fork or get rid of the bike. I think part of your problem is the gyroscopic effect of the heavier, larger tire and tube.

Oddly enough, retired framebuilder Dave Moulton who had quite a following in the 80s and 90s, built high trail road frames and people liked them! I was always intrigued by his bikes and wanted to try that geometry.

If I recall, Dave’s geo arrived at high trail via a combo of short fork offset and steep head angle?.. This may give an interesting sensation of steering stability, yet little flop. I’ve a couple of frames that seem to have these features, and they’re surprising decent on dirt roads even with 32 mm tires. They’re excellent on smooth roads. (For the record, I hate wheel flop, but I also like being able to ride no-hands to have a snack or pull off a layer, and don’t ride with large front loads enough to need a low trail.)

[NHAero]

There's a big difference in a 72 HTA with a 45mm vs. 50mm rake. My old Firefly had 72/50 and handled fine. I know I wouldn't like the BMC. My old '89 Casati had 64mm trail with a 73 HTA and a 38mm rake. I found that a bit slower handling than my other bikes but not objectionally so. My Anderson had similar trail with a 71.5 HTA and 55mm rake, and I couldn't bond with that bike's handling. So trail doesn't tell the whole story by itself. I like bikes with 73 HTA the best.

[prototoast]

Though I haven't ridden BMC, I personally like bikes with higher trail, and I'm glad that there are lots of different options out there in the market.

[Dave]

HTAs usually vary with frame size. I ride the smallest or next to smallest size in most brands. 71.5 is the most common and trail is usually in the 68-73 range. They all handle great with 28-30mm tires. It's just a matter of what you get accustomed to. The first rides on my Cinelli Superstar and 47cm Yoeleo R12 frames were great. Absolutely no complaints, but I'm not criterium racing with them. Steep mountain descents for me.

[nmrt]

Hah! I am glad someone brought this up. I have been noticing the high trail in the "racy" BMC's -- the Teammachines, since 2016-ish. They always had a trail in the 62-64 range for a size 54. And I was always puzzled because other manufacturer's racy bikes had trail in the 56-58 range for a size 54.

I've ridden the Teammachine and do not like how it handles. It is sluggish (yes, you may call it "composed" and love it) for a race bike for my taste.

But as Prototoast said, I'm glad there are those who prefer high trail in their race bikes and have found BMC.

EDIT: BTW, I have two road bikes. One with a trail of 62 and another with 58. I absolutely can tell the difference in how the front handles/steers between those bikes.

[spoonrobot]

Some people prefer to lean, some prefer to steer - within the bounds of what the machine wants.

I've attempted to understand where this subjective feeling comes from.

As much from the bike as it does from your inner ear and other anatomical balance mechanisms.

[NHAero]

Originally Posted by spoonrobot

Some people prefer to lean, some prefer to steer - within the bounds of what the machine wants.

As much from the bike as it does from your inner ear and other anatomical balance mechanisms.

Say more about the above please. I'm curious why we do have such varying preferences in how a bike handles.

[Spdntrxi]

I guess I am used to it...

Timemachine Road 62 trail
Teammachine R 63 trail

never notice any flop issues and lack of corner ability...

[rothwem]

Something weird I've experienced on my old Kona Jake the Snake is that its tricky to hold in a straight line when climbing a slow/steep road. The only thing I can point to is the long trail--its a 71.5° HTA with a 45mm offset fork, which works out to about 70mm of trail with 35mm tires.

That same bike is awesome downhill though, I have a technical gravel descent near my house and the JTS still has the Strava PR, even better than my FS mountain bike.

[NHAero]

Originally Posted by Spdntrxi

I guess I am used to it...

Timemachine Road 62 trail
Teammachine R 63 trail

never notice any flop issues and lack of corner ability...

I don't recall what size frames you ride. If they are on the small side, they'll generally have slacker HTAs to achieve toe clearance with the shorter TT length. If that's what you have always ridden, you've become accustomed to that handling (since really we're not talking about the difference between bad and good handling, but rather our sense of what constitutes good handling).

I'm on 55cm frames, large enough to be available in varying geos, and I know what I prefer, so I'm going to buy a Habanero rather than a Lynskey for an all-road stock Ti frame. In my size, the Habanero has a 72 HTA and with a Columbus fork at 52mm rake and the 650Bx42 tires its trail/flop is 55mm/16mm. The stock Lynskey GR300 has a 70.5 HTA and 45mm fork rake, for 72mm/23mm trail/flop. Many people prefer that GR300 and there's nothing at all wrong with that!