A lot has happened since the forefathers of mountain biking raced down the trails of Mt Tamalpais on their bling bikes. Hardly anyone would doubt that bikes today are worlds better and safer to ride than they were ten years ago. In addition to major innovations in add-on parts - suspension elements, disc brakes and tyres - there has also been a constant flow of changing standards. The head tube underwent many changes before it arrived at the conical shape that is common today. The bottom bracket still seems to be in the discovery phase. Only one standard has remained untouched over the years - the width of the hubs.
No matter how much the constantly growing number of sprocket sets and the addition of disc brake sockets have cramped the space on the hub - hardly anything has changed here. In the last five years there has been a change from quick release to thru-axles. But the effective width and all the associated dimensions (flange distance, chain line) have remained the same. Even if the figures suggest otherwise, a 135x5 rear hub has exactly the same construction and is just as wide as a 142x12 hub. This is demonstrated by how easy it is to convert most modern wheels between the standards. But with the ever-improving 29er bikes, the pressure of suffering grew steadily. The compromises in both wheel stiffness and frame construction became more and more obvious.
It is therefore almost surprising that the new Boost standard, which addresses precisely these issues, is triggering tirades of criticism. Of course, change hurts, and every new standard has to prove itself first. But at a time when bikers are constantly bombarded with new standards, the rejection is certainly also due to the fact that many people don't really know what they're dealing with when it comes to Boost. That's why we've taken a closer look at the topic and explain everything you need to know about the new Boost standard on the following pages. And for all traditionalists, the reassuring consolation remains for the time being: the new standard affects almost only the long-travel 29er and plus bikes. At least for the time being.
THE INITIATORS - Interview with Anatol Sostmann and Chris Hilton
Trek and Sram have developed the Boost standard in co-operation. What for?
Answer from Anatol Sostmann, Trek Marketing Manager:
Boost made its first appearance on the 2014 Remedy 29er. How did that come about?
We learnt from the 2013 Remedy that a twentyniner like this needs stiffer wheels. So we set out to find a way to increase their stiffness to at least the level of the 27.5-inch format. The only requirement was that we wanted to realise this with the existing Q-factor.
Was it just about stiffness?
Yes, at first our only goal was stiffer wheels. Then we realised that Boost can achieve further effects to make the 29ers even more agile and playful. Boost allows us to make the rear triangle of our 29ers much more compact.
Why is Boost only found on 29ers?
Boost was born to optimise our 29ers. The benefits are clearly noticeable there. With Boost for smaller wheels, we do not yet consider the cost/benefit ratio to be ideal.
Chris Hilton, Sram - Product Manager Drives:
What are the advantages of Boost?
Boost primarily brings new design freedoms. It simply allows better bikes to be built - with more tyre clearance, such as plus bikes. Bikes with stiffer and more compact rear triangles, but also with optimally positioned pivot points. We have already embarked on this path with our 1x11 drivetrains and are consistently pursuing it with Boost. The Q-factor remains untouched, because with our Boost cranks only the spider or the chainring changes, but not the crank arms themselves. It is important never to mix standards. Boost only really makes sense as a whole and with a suitable Boost-compatible frame.
What are the benefits of Boost for the wheels?
The additional stiffness through the use of Boost hubs is enormous - between 17 and 33 per cent according to our measurements. At the front, you can feel the additional stiffness due to the ten millimetres more than at the rear with only six additional millimetres.
Cristian Artmann - Bike test editor
I think Boost is a step in the right direction. The long overdue design approach addresses several problems at once - stiffer wheels, more tyre clearance and more options when designing new frames are good arguments for me. My previous experience with Boost bikes confirms the benefits. However, I wonder whether an untouched Q-factor is really worth going only part of the way at the rear. You would hardly notice a few millimetres wider crank, and the technical advantages could be used even better. I mean: Boost is more utility than hype!
...
1. what is Boost 148 anyway?
A little wider please: The new Boost standard applies to hubs and cranks and cannot be retrofitted to a conventional bike. The rear triangle and fork must be designed for the increased installation width. The aim is to increase rigidity and tyre clearance.
Boost itself is not much more than an open standard that Sram and Trek have developed together. The rear hub increases in width from 142 to 148 mm and the front hub from 100 to 110 mm. At the same time, the chainline moves further outwards, which is why Boost also requires adjustments to the cranks and chainrings. However, the crank width (Q-factor) remains unchanged.
2. what does Boost have to do with Plus?
For many bikers, "Boost Standard" and "Plus tyres" are interchangeable terms. Why?
It is no coincidence that Boost and Plus bikes appeared at the same time and are therefore often equated: Boost creates the necessary space for the three-inch wide plus tyres on many plus bikes. However, there are also plus-capable bikes that manage without Boost, at least at the rear (e.g. Last Fast Forward). Therefore: Boost is predestined for plus-size bikes due to the space gained. But it is by no means the only way. On the fork, however, Boost is a real must for plus bikes. Only the latest generation of suspension forks with 110 mm axle width offer enough space between the bars for tyres up to three inches wide. The previous forks are simply too narrow for this.
3. what are the benefits of Boost 148?
Boost aims to kill two birds with one stone. Stiffer wheels and more space in the bottom bracket area, where it was previously extremely tight. But how much difference does it really make?
The wider hubs make the wheels stiffer and - if you believe the manufacturers - more durable. The stiffness is primarily due to the wider flange spacing of the hubs, which increases the spoke angle. Our comparative measurement on a Sram Roam 40 wheelset (see diagram below) confirms this. With Boost, the 29er wheels, which are sometimes criticised for being too soft, only reach the stiffness level of comparable 27.5 mm wheels at the front. At the rear, the stiffness increases by ten per cent, but still lags behind the values of the 27.5 counterpart. The second advantage is that the longer chain line on the crank means that there is more space available in the chronically cramped bottom bracket area. This can be utilised in different ways: Firstly, to make the rear triangle more compact, see example on the right. Or to maximise tyre clearance, such as for plus bikes, see point 2. In addition, the space gained through Boost can also be used to make the rear triangle stiffer - for example by using larger bearings or a wider support.
4. where is Boost relevant at all?
Unlike the switch from quick release to thru axle, Boost frames and components are no longer compatible with the previous standards. Converting current frames to Boost wheels is not possible or only possible with a new rear triangle. Although the first adapter solutions also allow standard wheels to be fitted to Boost frames/forks, their usefulness is questionable. Therefore: If you want to build a bike with Boost, you need new wheels or hubs and have to adapt the cranks. Otherwise, Boost is less of a conversion issue than one that is primarily important when buying a new bike and, for the time being, almost only for all-mountain 29ers.
5. what distinguishes the Boost dimensions from the downhill standard 150x12?
The downhill standard, also known as 150x12, actually has a centre distance of 157 millimetres. In order to accommodate the additional 15 mm in the frame compared to the previous 142 mm wide hub and to maintain a practicable chainline, cranks with a wider Q-factor would also have to be used. This is a particularly sensitive issue for CC and endurance bikers, which is why the unchanged Q-factor was one of the targets for Boost. According to Sram, the 52 mm chainline from Boost is the widest possible hub design that can still be used without changing the Q-factor.
Boost - a different interpretation
Sram's template is clear: The hub flanges and thus the total width of the hubs are moved outwards by equal amounts on both sides - by 3 mm at the rear and 5 mm at the front. But there are also ways to utilise the additional width differently.
AMERICAN CLASSIC Boost - the Symmetrics
With its Boost hubs, the US wheel manufacturer is focussing on more symmetry in the wheel, or rather, on balanced spoke angles and tension between the two sides. "With the usual interpretation of Boost, you get a statically stiffer wheel, but retain unequal spoke tension. Durability suffers. If the wheel is symmetrical, the static stiffness increases less, but the spoke angle and tension can now be equalised on both sides. The positive effect of this is more noticeable in practice and also ensures a more durable wheel," explains Bill Shook from American Classic. For this reason, only the disc mount on the Boost rear hub is offset 6 mm further outwards. The newly centred rim results in an almost perfectly symmetrical wheel. At the front, the standard hub shell is even used and the hub is only spaced out to the right - with the same symmetrical result.
SYNTACE/LITEVILLE EVO6 - the forward thinkers
Syntace/Liteville is taking the Boost approach even further with the open standard EVO6. The whole thing is based on the width of Boost and utilises an asymmetrical rear triangle construction for wheel symmetry. Similar to the Cannondale FS-I hardtail, this requires special frames that only Liteville has built to date. Instead of going 3 mm wider on each side, the rear hub of the EVO6 and thus also the chain line is shifted a full 6 mm to the right. This allows the wheel to be built symmetrically again and at the same time utilise the entire available support width of the Boost hubs for wheel stiffness. "We compensate for the 3 millimetre shift in the chain lines compared to Boost with the low manufacturing tolerances and high rear-end stiffness of our bikes. We have tested EVO6 extensively for a long time and found no disadvantages," promises Jo Klieber from Syntace/Liteville.
