Geometry Primer

Tight cornering and turning is based much more around trail, handlebar width and individual rider skill than wheelbase, IME/O.

I think this is partially due to mis-attribution due to a lack of understanding how small changes in the first two variables have more outsize effects on the feel of a bike much more so than wheelbase. Especially during high speed and aggressive movement of the bike/rider. Something like ~7mm of trail and corresponding ~2-3mm of flop can have a very large effect on how a bike feels as it begins to lean over. Conversely, when riding blind I’ve found most riders have a hard time differentiating less than 20-40mm of wheelbase change, especially if it’s balanced on both the front and rear end.

Looking at the bikes that finish DK is interesting but most people do not understand geometry well enough to have had it be a defining factor in what bike they choose to purchase/ride in comparison to all the other variables involved. It takes quite a bit of $$$/experience to really suss out the small changes and their effects.

I will also say that the terms relaxed and aggressive are poor descriptors and do not describe how a bike rides. It would be better to describe bikes along a spectrum as:

Use steering to turn or maintain a straight course, leaning and body english produce much less reaction and are much less necessary. Also has less stability at the front end as the speed increases.

or

Use leaning the bike at an angle, counter-steering (push handlebars inside of the turn) and body english to turn or maintain a straight course, steering with the handlebars produces much less reaction and is much less necessary. Also has more stability at the front end as the speed increases.

Low Trail 35mm
Steering, less stable at speed

Mid Trail 55mm
Balanced steer/lean, stable at speed

High Trail 70mm
Leaning/countersteer, very stable at speed

Note: larger tires, more aggressive tread and lower pressure all increase trail for a given geometry. Wider handlebars provide more leverage and increase feedback on low trail, too wide creates a nervous descending bike that is overly sensitive to small corrections – oversteer condition. Narrower handlebars do not have enough leverage and decrease feedback for high trail, the bike is hard to maneuver during descending and resists cornering – understeer condition.

Personally I find high trail bikes extremely hard to corner with handlebars less than 52cm wide. Even then they require a significant amount of leaning and benefit from very aggressive side knobs to prevent sliding at lower speeds than lower trail bikes. Conversely I find low trail to be much too nervous descending – compared to mid/high trail, smaller rocks and road features tend to wrench the front end around requiring significant focus to make corrections to track the preferred line. Mid trail is my preferred front end geometry as it has a good balance of steering/leaning and although it lacks the stability of high trail on rough descents at very high speed it is still acceptable for the additional ease of cornering.

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