TLDR: The RR stem gives more consistent front end loading, over a traditional stem as you steer and counter steer for balance. You need to setup the front for the level of load it gets at neutral to get good traction. A long chainstay gives a smaller differential between max load on the front and neutral load relative to a short chainstay making front setup balancing support and traction easier.
While front center/rear center ratio is important, it’s less crucial than good setup for front traction. My very first customer from a few years ago is a big 350lbs 6’6” rider on an S6 Levo with a 532mm reach, 442mm chainstay and ~1.98 f/r center ratio. He loves his RR stem particularly flat cornering which is its biggest benefit to me and many of my customers, and he’s on the taller Gen 1 150mm RR stem that puts you even further up and back away from the front end. Along with that, I spent a lot of time originally developing the RR stem on a M/L Trek Slash that had a ~1.84 f/r center ratio again with the Gen 1 150mm RR stem among many other bikes with even higher f/r center ratios.
I’ve even gone as far as a ~2.175 f/r center ratio on my prototype Mule TR frame with a 569mm reach, 423mm chainstay, and 1343mm wheelbase specifically to test if you really needed a super long reach to work with this, and if a reward weight bias would really be an issue with it. That bike was super rear biased, and horizontally with the Gen 1 150mm RR stem my hands were further behind the front axle than my feet were from the rear axle as you can see in the picture. That bike used a very soft fork and front tire pressure relative to my weight and tended to have the rear drift out with a front end that was very eager to change direction and turn. It was very fun to ride, and surprised me how much I liked it.
A lack of front load is not typically what leads to the front washing out and much like with cars, too much front load leads to understeer aka front pushing, and too much rear load leads to oversteer aka rear drifting. The difference is that on bikes we also have to balance standing up and falling over. This is actually where the bigger issue is. When you are cornering, and you can’t feel and keep your balance point by effectively steering and counter steering, you can start to fall over which unloads the tires which are the only thing keeping you turning. This leads you to instead continue going straight as the object in motion that you are while you fall over which looks like the front suddenly washing out.
On a forward offset stem, your hands move side to side substantially as you turn the bars felt as wheelflop. Unless you are staying right on top of that motion by weighting the bars, this can make it harder to keep your balance point loading into your tire instead of moving off it to one side or the other. This is part of why riders tend to like low bars with a long stem and feel they need to keep say weight on the hands.
With the RR stem, your hands are much closer to the contact patch of the tire along the steering geometry, so they flop side to side less and keep you more consistently over the tire when balancing. This allows you to ride more through your feet with no weight in your hands while keeping good feel for balancing. With all your weight through your feet at neutral, you setup the fork to have optimal traction with zero hand load and then can always add load from there as needed. When you setup the fork to handle optimally when you are loaded say 20% on the hands as your neutral, then any amount less than that has the front underloaded with poor traction. This means that you have to always be optimally loaded at the hands or more for the fork to have optimal traction instead of optimal traction already being the baseline even with no load for a more consistent feel for traction.
Chainstay length comes into play also for consistency of front loading. Generally, I prefer a very long chainstay like on my current favorite Mule EN with a 445mm reach on a 697mm stack, and a 507mm chainstay for its also 1343mm wheelbase giving a ~1.649 f/r center ratio. The main potential advantages of a short chainstay are that the front wheel is much easier to lift, the rear wheel is easier to place, the bike can make very quick short direction changes very easily and quickly, the rear gets overloaded to carve and shralp easier, and generally they can make the bike feel more playful and fun. The main disadvantage of the super short chainstay is that it’s less stable, and can be a bit too eager to change direction leading to a more darty feeling and less settled front end which can also be quite exciting. Also, the front has less weight on it at neutral position, but the same weight on it at max loading, so balancing a fork and front tire setup that gives great traction and support is a bit harder. A long chainstay gives a more consistent front loading because it goes from say 100% load to 40% load at neutral where a super short chainstay may be like 100% load to 30% load at neutral.
All f/r center ratios that you will find on any bike will be between the two extremes I’ve run and found can work great with the RR stem so long as you get the front end setup well to work with its range of loads when riding with all your weight through your feet. The long chainstay just basically just makes getting that consistent front end feel and setup easier to achieve.
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Have you made any adjustments to front tire and fork pressure yet?
If all that looks good and it feels good, then you probably don’t need to change anything further until you find a need or want to experiment. Don’t be afraid to experiment though. You never learn if you don’t experiment.
The main one is the tuned Reversed offset for best steering dynamics. The Raised height is the second big factor for improving body position and helps the Reversed offset work with modern geos. The changes to suspension and tire setup for that change in body position brings it all together, and that can be furthered by pairing the bikes geo to it. Just doing one without the others only gives a partial view of the whole concept. The more parts you can get, the better it will be, and it works best when they are all together.
